Week 6 flower, Top fan leaves starting to turn yellow. Need help asap

So over the last 2 weeks, two of my plants were starting to show deficiencies. The top leaves are starting to turn yellow. I thought it was potassium at first. Was feeding 1/4 recommended amount for Part B then upped the nutrients to 1/2 recommended. My ppms are now at 1200 when I'm feeding, Ph 6.5-6.8 and the problem still seems to be getting worse. The light sits about 1 1/2-2 feet away from the plants and the temperature is between 68-76 with humidity sitting between 50-60%. I haven't been using much of the part A solution so I'm wondering if it could also be calcium magnesium. Ppms of my run off are 1400 and the ph is between 6.5-7. Usually I will feed Twice every other day and then flush thoroughly with RO water Ph 6.5.

Amount of Nutrients used per feeding:

Part A 1/6-1/4 recommended
Part B 1/2 recommended
Big bud 1/2-full amount recommended
Nirvana Full amount recommended
B52 1/4 recommended
Carboload 1/2-full recommended
budcandy 1/2-full recommended
X-factor 1/3 recommended
Overdrive Haven't used yet
Calmag 1/6-1/4 once every week or two
Sensizyme 1/2 recommended

The strain is Ice Cream Cake, indica dominant hybrid.

Sorry for the late ass response but as u probably figured out that is what supposed to happen..any pics