Anyone have a few minutes to help out a hydroponic noob?

I started out using 6.5 PH water. After nearly killing my poor girls the helpful lads at the hydroponics store in my area told me Soil and Hydro don't use the same PH, imagine that.
Anyhow, they were off to a rough start. With some careful 5.7 PH watering and flushes they really started to take off, now I feel as if I am starting to see the growth slow down and they are showing a few signs of damage. Please help if you have some experience in hydroponics.

Apologies for not searching through the forums before posting this. I am going to start trolling them now, but I really don't know exactly what to look for. >.<
https://www.rollitup.org/blogs/blog25244-help.html

They look a little burnt to me, this could be causing lockouts whats your ppm like?

thats burn. read the "plant problem diagnosis" sticky