locked up

Hello All.
Plants have spots appearing and mottling developing on top leaves, then turn yellow. If I have locked up my plants roots what should I do? I have flushed the plants through and tested the run off and it came out at 6.0 (too low?) Into 12/12 at 33 days into flowering. generaly they look good. First timer and I am unsure what to do.
Any input would be great.
regards afro.

run with clearex and straight water from here on out

Thanks for reply.
I flushed 20 mins ago with ph water at 6.6.
I won't water till tomorrow, but with straight water at ph 7.0. No more feeding, is that right?
Thanks Afro

i would go a week with no feeding and see if you can get them in better shape. then maybe 1 week of feeding then 2 straight water