Leaves of seedlings turning yellowish with whitish spots


Can someone please help this first-time grower? The older leaves on my seedlings are turning yellowish with much lighter spots. I hope the pics will show it. There is no burning on the ends of the leaves… yet.
These are Gold Leaf and are 13 days old today. They are planted in the soiless coco based grow med in the first pic and have not been fertilized. I have been putting them outside in the sun during the day since they were about 5 days old and inside under a T-5 grow light at night. I water them with rainwater with a PH of 6.8. The temperature is 78 when they are inside. Outside varies and they are in direct sun for most of the day. Eventually, they will be outside all the time.
In the picture where all of them are shown, the one on the far left is a WW and has never been outside. It is several days younger than the GLs.
Do they need fertilizer? I was under the impression that they shouldn’t be fertilized until they are 30 days old, so I have not given them anything yet.
I would appreciate all the help I can get.


Did you possibly get over spray on these plants when they were smaller?

The spots could be from placing such a small seedling in direct sun. Sun scald or bleaching could occur.

Looks like you have a soil mix that would not require further nutrients to be added, and NO; You should never add nutrients to small plants until they have an established root zone.

IMO Coco = Bad idea.


I don’t know what you mean by overspray. Spraying something else that got on them? There has been nothing sprayed around them. I thought about it might be the sun, but what about seedlings that are started in the ground outside and are in the sun all day? Why would that be any different?
I have read where Coco is not a good idea and others swear by it. I wish now that I hadn’t used it, but it’s too late now. So you wouldn’t recommend any fertilizer at this point? Thanks, latewood.


Also just to point out if your using coco your ph is way to high at 6.8 that could be all your problems there.

Coco needs a ph of 5.8


Shouldn’t the pH for coco be 5.8?


Yes you caught my typo thank you @GrowManFitz


So I should be watering them with a lower PH? The rainwater I was watering them with was 6.8 so maybe tapwater woud have a lower PH. The only thing I have to check it with right now is PH test strips for fish tanks. I have a PH meter ordered but it won’t be here for a couple of days.
If the PH is too high does it cause the yellowing with the light spots? Thanks, @GrowManFitz, @Majiktoker


Yes it will cause all sorts of problems, because once a ph get too high or too low, it will begin to lock the plant out from absorbing nutrients it needs.

More than likely your tap water won’t be any lower, unless you are on well water, but city watwr usually runs about 7.0

Yes you should be watering with a ph between 6.1 and 5.6 I belive is a good range for hydro. 5.8 is the sweet spot


So I need to add a PH down. I’m supposed to get that with the meter. Is there something I could add until then? Thanks @Hawkeye_diesel.


You could use sulphuric acid during veg and phosphoric acid during bloom. Sulphuric acid is nothing more than battery acid which you can buy at Autozone or pretty much any parts store. Just add 17ml to 1L of water and use that as your pH down solution.

In a pinch you could use white vinegar. It won’t buffer the pH for as long though.

Also, when testing your pH you want to test the pH of the water going in, as well as the runoff. The runoff is a more accurate picture of what the pH is at the root zone… where it really matters.


Thanks, @GrowManFitz :sunglasses:


for @Lornakins

I have thoroughly enjoyed this thread and have learned a lot. I too am a 72 year old granny starting my first grow, @Countryboyjvd1971 and @Hawkeye_diesel and a couple of others have responded to my 2 threads that I posted. This thread is amazing. I’m still needing help on my last one that is Leaves turning yellowish with whitish spots. I have just gotten the growers kit that was recommended to me which contains the PH pen, the humidity and temperature gauge and the TDS gauge. I got what I thought was a bottle of calculating fluid for the PH tester, but it doesn’t say anyhing about what PH it is. The directions say to adjust calibration so that the meter indicates the correct EC or PPM… HUH?? I don’t understand that. How am I supposed to know that? I have included a picture of the bottle. This is probably not where I should be asking this, but since I have read this whole thread, I just want to say that @Bobbi, I think you are awesome and I love the way the guys have helped you so much. You are now my role model… lol!! I am hoping you have a great harvest after all your work. :heart_eyes:

moved from

Sick seedlings 3/4" tall

@Lornakins I’m a 57 year old grandfather myself and I enjoy helping out. Lord knows I have received an immeasurable amount of help here too and I like to pay it back or forward, however you see it. It’s great when you see folks you have helped giving advice to others! and I’m sure the guys that helped me out get that same tickle!

Unfortunately, I am going out for the day so I can’t answer your question right now. We are off to visit my sons and 3 grandkids for the afternoon!

I will try and get back in here later this afternoon, but I wouldn’t be surprised if you have already gotten the answers to your questions from one of the others!


Oh, no hurry, Bob, enjoy your visit with your family. I will be taking some more pictures and posting them some time today with more questions so plenty of time here. Thanks so much Bob. :relieved:

Here are all my girls today: The 4 on the right are the GL and are 16 days old today. They are in coco coir, pictured in OP.
The 2 on the left are WW the bigger one is also in coco coir and is 13 days old.
The smallest one on the left is only 6days and is in FFOF.
I have have not been able to calibrate my PH tester yet. I have a feeling that I probably need to flush these gals but I’m not sure just how to do that and then I need to get the PH lowered. Here is the stuff I got to calibrate with, but it doesn’t say what the PH is and says to adjust calibration so that the meter indicates the correct EC or PPM… HUH?? I don’t understand that. How am I supposed to know that?
I will save the other questions for when I have this resolved.
@Countryboyjvd1971 your help would be greatly appreciated. I know I’m a dummy and I hate that I have already messed up so much, but I need to learn. I’m hoping that these girls can be saved.
I have stopped putting them outside in the sun, as some have said they were too young for that so I messed up there too. :worried: Oh, woe is me!

And I plan on putting 3 of the GLs and one of the WWs outside permanently in containers. The other 2, 1 WW and 1 GL I will grow inside. More on that later.

This will be delivered tomorrow.


That solution is for calibration of tds meters not ph meters sorry but you’ll need to get ph calibration fuild most of us use a7 ph calibration fluid can get on amazon @Lornakins
The ones in. Coco will need ph of I think it 5.8 but you’ll need to confirm that you will treat it like hydro
the ones in ffof will need 6.3 -6.8 ph water
Hope this helps
Happy growing :smile:CB


That helps a lot, CB. Do you think I should flush the girls that are in the coco since I have been watering them with rainwater that tested 6.8 with fish tank test strips? I watched a youtube video and the guy calibrated his PH pen with white vinegar which he says is definitely 2.4, so I calibrated mine in that. Then when I tested my rainwater, it was 6.4. I have a huge pond 1 1/2 acre in my yard with a lot of fish in it so I thought it might be good to water them with, but it tested 7.4… gah!! My well water is 7.4 also and my tapwater is also 7.4. I get my drinking water from a local spring and it tested a whopping 8.5! So I have no suitable water on the place without making adjustments to it. The rainwater will work for the one in the FFOF, though, but for the others that are in coco… no! So it looks like I will be using adjusted rainwater since it is the lowest. But I won’t get my PH kit until tomorrow. Do you think the girls in coco will be ok till I can give them some adjusted water? I am just beside myself! :weary: Thanks for your help! :+1:


I’m not sure you need to flush but adjusting you ph for coco should help just water till you get run off
My well water is high ph also and high ppm around 300 ppm and 7.3 ph
I just use ph up and ph down
I also collect some rain water and use that on outdoor grow since my green houses are about 2 acres away from the house with no running water
And it doesn’t need to be adjusted unless I’m feeding then I still need to ph up cause nutes lower ph so much
Sorry for the long delay in my reply


Ok, thanks, CB will do. Is the ppm important and do I use the TDS meter for that? Do I need to calibrate it with the stuff in the bottle that you said is for the TDS meter? This stuff is all so confusing and perplexing for me. When I started this, I had no idea what all is involved and how complicated it really is.
I will be getting my PH kit today, so I can start watering them with properly adjusted water.
Since the feeder leaves (I forgot what they are called) are turning yellow, do I need to start nutes on those?


I will say yes on starting nutes on ones that the feeder leaves are falling off
And yes you would use your TDS meter to check ppm of you water so meters need to be adjusted some will auto calibrate or are factory calibrated
You can check the meter with you solution it will tell you if its accurate
Yes ppm is important and with a high ppm reading you should adjust you nute mix to cominsate for that
It helps if you know what minerials are in the water but if your using rain water I’m sure your ok
I follow Foxfarm feeding schedule I use the dirty dozen line so almost the whole line up
I only feed once a week at full streaght myself
I’m only passing on my experience here
I know there’s a lot said about starting slow with nutes youll need to make that decision for yourself tho


My TDS meter says it is factory calibrated to 500 us/cm so should that be the reading when I put it in the solution? Is there a table that tells you if your reading is high and nutes need to be adjusted accordingly? I’m sorry I’m so stupid about all of this. I know I’m a PITA and I am so thankful for your help.
So you get your nutes from FF? Can I order them on Amazon?
I will be using my rainwater so hopefully, I will be ok with the ppm.