Feeding question.

[Hops]

I read on a website that I could grow using a soiless mix. I bought some promix, and fed using quarter strength nutes. I'm on my 4th grow. But each time, after 3 weeks of flowering, my leaves really start to yellow. Eventually they all yellow then the plants done around week 7 - 8. But, I can't get over why the hell all my leaves yellow when I see some nice grows here where the leaves are soooooo green. I am running a 400 hps. The temp gets around 81 to 82 degrees. I have a cheap duct fan, I'm waiting for my vortex to come in the mail, which should bring the temps down considerably.

I use Grotek 2 part. I water quarter strength about twice a week. My mother plants look beautiful. I haven't did a Ph test, but I was told that using straight promix you can water without checking. My ph out of the tap is 7. I'm going to start leaving the water sit for 48 hours from now on. But can someone just tell me if my feeding schedule makes sense? I tried upping it once and burnt my plant seriously...

Thanks.

Hops.