K Deficiency? Need other opinions

Media: Fox Farm Ocean forest potting soil in 2 Gal. Fabric pots

Light: 300w Vipaspectra LED 20/4

Nutrients: Fox Farm Trio on suggested schedule.
I think for the most part I have this figured out. I’m just wanting other opinions from people more experienced than myself. Around a week ago I noticed the older leaves on my plant starting to yellow on the edges.

At first it was only on a single leaf so I wasn’t too worried. But soon I saw it spread to a few more. I also noticed that the tips of my leaves are burnt characteristically resembling nutrient burn. This led me to believe I had a lockout. I do have a pH test kit unfortunately I do not have a PPM meter. But I always pH test the food going in at 6.5. I went ahead and decided to flush her. upon test of her first runoff it read 6.6 which confused me because I figured with a lockout and nutrient burn it would have been much higher?

This is basically what I’m needing confirmation on. Now that I have her flushed I need to get down to what nutrients she wasn’t able to uptake and make sure she has them.looking at other guides my best guess is that this is a potassium deficiency. Can I get some opinions from other eyes? Thanks.

FFoF is very rich in nutrients and microbes. If soil is very wet the lower leaves can get N toxicity. (Blotches) I wouldn’t worry about it unless is spreads to entire plant.

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Good to know. The nutrient burn I was seeing was all over the plant. While a select few where the picture above. Thing that gets me is with nitrogen doesn’t the yellow star at the tip of the leaf and reseed downward? I don’t know she’s got me all confused LOL

Are you using any Calcium, Magnesium, or other micronutrients?

How old is your plant?

Definitely not a pH lockout, b/c 6.6 is a good reading.

Also, how did you flush?

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I think there are amounts of both in fox farms big bloom. Day 47 week 3 of flower.
Flushed using 3x pot size of pure water.

I would venture to think you have a calmag issue too. Hard to say without ppm reading, but big bloom isn’t a complete nutrient line. Your runoff ph seems to be within range, and 47 days is long time to go on amended soil.

After you flushed, did you feed?

As pointed out, there’s some N toxicity showing too.

After flush i did feed at 3/4 normal strength.

Do you mean too much calmag? Or not enough. I haven’t used anything bust FF trio.thanks for all the help guys!

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I thought with nitrogen toxicity leaves turn dark green curl downward and have a shiny tent. Which doesn’t really describe this girl. As far as looks, most the leaf tips are very slightly burnt. While around 15% of the fan leaves look like the ones pictured above.

I would say not enough magnesium. But that’s thumb eyeball diagnosis. Do you have tds tester?

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I do not. Could someone link a good recommendation?

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Just studied up on magnesium a little bit and the symptoms are much more accurate to what is happening to her. So that’s very possible. Something I’m not sure about, when I flush does my water need to be PH’d? Like should it be in the 6.0-6.5 range as well? Sing some info that says yes, but to me that doesn’t make sense because there’s no nutrients in the water to take up in the first place so why would it need to be PH’d?

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Maybe just seeing it with blurple


Always check pH and adjust accordingly, even when just giving plain water.


So it’s okay to flush with water that’s had ph up or pH down in it as long as it gets to that 6.5 range?. Because my tap water I use is very alkaline

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That’s exactly how you flush, using plain, pH adjusted water. :grinning:

I highly recommend an ec/tds meter to check your tap water, feed, and run-off, as well.


The only one I have kinda sucks, but it does give you ballpark results. I would see if someone else has one they are a little more confident in.

Went ahead and ordered some Cal-Mag and a ppm meter. Next flush is tomorrow for the girl in question(back left). She still looks good over all.

front plant on final flush for last 2 weeks so thanks for the info on flushing @blackthumbbetty

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