Yellowing and brown spots 3 weeks into flower

ShaggySparx · February 19, 2020, 11:24pm

I’ve been following a popular youtube grower, not sure if I’m allowed to mention who lol, but you may know when i describe it. He uses FFOF and only waters with RO water, liquid seaweed extract and molasses and a compost tea every few weeks.

So I think I’m having a nitrogen deficiency. Started with the fan leaves getting lighter about a week into flower, and 2 weeks later, today, the fan leaves are VERY yellow and getting brown spots and the sugar leaves are starting to yellow too, Buds are developing but no trichomes yet. Problem is it’s a random auto so i don’t know what genetics or tolerances it has. PH going in is 6.8, runoff is between 5.5-6.0

Any ideas what i should check?
Can i add a micro dose of N?
If i can’t find a solution, can i harvest at the first sign of trichomes? i obviously would smoke it if its prematurely harvested, but would the cannabuter i plan to make be effective?

Drinkslinger · February 19, 2020, 11:28pm

Your runoff is too low. You want it to be around pH 6.5 ± .3 for soil.
Try upping the pH going in.

Also, using Ro or distilled water ususlly leads to calcium or magnesium deficiency.

You can top dress with some growers lime/dolomite lime. It’ll add calcium as well as buffer the pH.

ShaggySparx · February 19, 2020, 11:28pm

2 different leaves from 2 bud sites

ShaggySparx · February 19, 2020, 11:37pm

Thanks for the quick reply. On my 1st grow i thought that was the case so i flushed my 3 gal fabric pots ph’d at 7.0 and 30 gallons later the runoff finally went up from 5.5… to 5.9 lmao! Forgive my ignorance but how high should i go to try to regulate it?

Also added some dolomite lime 2 weeks ago.

Hellraiser · February 19, 2020, 11:44pm

Your plant is starving, I’d feed her some complete flowering nutes and cal mag, not too late to turn her around to finish.

Drinkslinger · February 20, 2020, 8:28am

Are you keeping track of ppms in/out? If so what are they?

How recently did you flush? Did you flush because the leaves were yellowing, or because the runoff was too low a pH?

How much lime did you add, and what size container?

Just trying to gather information so we can give the best advice.

HornHead · February 20, 2020, 12:21pm

Happy birthday/anniversary @Drinkslinger

MrPeat · February 20, 2020, 12:50pm

Happy B-day @Drinkslinger

Looks like you got this under control.

ShaggySparx · February 20, 2020, 3:36pm

around 850 ppm going in, 550-600 coming out. I have not flushed this batch yet at all and i added 3 Tbs dolomite for 3 gallons

Drinkslinger · February 20, 2020, 5:20pm

The ppm # show she’s hungry.
You can use up to 2 tbs dolomite lime/gal. It will take at least a week to make any difference.

I’d get a batch of tea brewing asap, add a little extra N to the brew (blood meal works great), be sure to adjust the pH high before feeding (I’d push it to pH 7.5).

A day or two after the feed do a slurry test on the soil. Take 2 tbs soil from around the root area, add to 2-4oz or distilled water, mix really really well, let sit for 15-20min, then test for pH. You could do a test now and then later to compare.

ShaggySparx · March 14, 2020, 5:59am

Sorry i did respond but i guess it didn’t go through. I flushed her out, added a little N with some tea and fed her through the soil and also foliar with diluted tea. The yellow leaves actually bounced back to green about 2 days later. Brown spots are still there but the newer leaves are spot free with the exception of a few that look light bleached or something, even though they aren’t the closest leaves to the light, you can kinda see in the 1st pic. I’ll get a clearer one tomorrow.