Help Identifying problem/solution

I think I could use a little help with this problem. I am stumped because its only happening to about 1/2 of my garden. Take a look at the pics. This has been going on for a few weeks now but getting slowly worse. At first I thought some 1/2 strength nutes would help but it didnt change anything so Im guessing its a ph problem. I tested the ph with a meter when the problem 1st occurred but it seemed ok (6.7ish)

The setup:
-Indoors
-Soil is a mix of about 40% fox farm - ocean forest, 40% coco fiber (coconut fiber) 20% pearlite.
-temp is pretty steady with about 75 F
-humidity steady from 40%-60%
-Watering every 4-5 days but I admit I have forgotten like 3 times and they had started to droop but after watering they seemed fine. :confused:
- for the most part I have treated all the plants the same but for some reason 1/2 are fine and half are yellowing at the top (see pics)
-strains some PK and some chemdawg
-They are in about the 7th week of veg. but before that I had lousy soil that was causing major lockout/drainage/ph issues so I transplanted to this new mix.
-1000W HPS on 16 hours a day schedule inside a grow tent


They all were doing fantastic until about 2 weeks ago now growth has slowed more on the yellow plants but all seem to grow slow now.

Any advice would be a great help as this is my 1st non closet garden.
 

Attachments

Top