yellowing problem

[shoulderpain]

I have been doing great for my first time but have run into a little snag. I am getting yellowing. the research I did I am coming up with sulfer or sulfate problem, I went ahead and flushed the soil with 6.8 ph water.
does this look or sound like I am doing the right thing. thank
by the way, I they have been in flowering for about 3 weeks

[shoulderpain]

here are a few more pics