Plant is in trouble but not sure what kind -- Please help

[tiger87]

My grow (only my 2nd):
heavyweight fruit punch feminised
soil: FFOF
nutes: 1/4tsp per gallon twice since I started (FF grow big)
8 weeks in veg
currently on 15th day of flower
using 2 150W LEDs
3' by 1.7' 5.5' tent with 250CFM exhaust fan
78F during lights on 66F lights off
35% humidity (was 65% for veg)

When the leaves first started yellowing (I assumed this was nute burn) I flushed. things looked okay so I started a regimen of nutes (about 4-5 weeks in). After the second feeding I started noticing more "burning" so I stopped the nutes and flushed ~1 week before I switched to flower. Plants looked okay for a little while, but have been getting progressively worse. I flushed again a few days ago, but now I am not so sure it is nute burn and don't really know what to think. See pictures below and any advice will be greatly appreciated. I am going to try to get something to measure pH today... will update when I know more on that front.

 

[PeytonManning]

Looks like lockout from pH imbalance. Maintaining proper pH is one of the most important aspects of growing. You'll probably need to add cal/mag to your feedings too

 

[MassMedMan]

I swear I see some of that early leaf problem on my plants... gonna watch this. Good luck, please let us know what you do and find out.

 

[tiger87]

Looks like lockout from pH imbalance. Maintaining proper pH is one of the most important aspects of growing. You'll probably need to add cal/mag to your feedings too

A decent digital pH meter isn't in the budget at the moment so I had to use drops. My tap water is ~7 and my run off is ~6 so I figure my root zone is between 5 and 6 (is this a fair assumption?)... "lockout from pH imbalance" is looking like a pretty good bet.

I picked up some pH up/down, CalMg and TigerBloom. What should be the target pH of my water to get pH up to the ~6.5 sweet spot? ... or should I flush until I get it up to the right level then feed with properly pHed water?

Thanks in advance

 

[PeytonManning]

I don't grow in soil, so I'm not sure how they balance it out. But a decent pH meter can be had for 15 bucks online. Might wanna put it on the Xmas list

 

[tiger87]

Update:

I tested the run-off of the original soil (still have about a 1/4 of the bag left) and it came in somewhere between 4-5... does FFOF usually run that hot or did I just get a shitty bag?

 

[PeytonManning]

FFOF is always hot. Most people try to mix it down with happy frog or light warrior

 

[Dave Groomer]

Update:

I tested the run-off of the original soil (still have about a 1/4 of the bag left) and it came in somewhere between 4-5... does FFOF usually run that hot or did I just get a shitty bag?

I use 1 part FFOF, 1 part Promix BX and 1 part perlite and my clones and seeds seem to be doing fine with that. When I first got the FFOF, I used it straight and got minor nute burn but I was all over it right away and I flushed the heck out of the clones (they were in solo cups at the time so not a big deal.) Then I got the Promix, cut the FFOF and ttransplanted into bigger pots and all was well.

Supergroomer