Yellowing leaves. Just transplanted to DWC

I just transplanted white widow from solo cups into DWC with nutes and balanced pH. Most of them were close to root bound so I can see the transition has helped in that way, but the lower leaves on some of them are starting to yellow, and some of the healthy green leaves have tips that look a little burned.

Grow room is 6' x 8' with one 400w MH Fixture
and four 4' flouros. I have 3 separate DWC
hydrofarms with air stones and six plants each.

Any help???

How high is the water level in the hydrofarms?

When I transplanted to DWC, I had the same problem. In my case, the roots in the hydroton were drying out. I poured some ph'd RO water over the hydroton and they perked up in a few minutes. I did this a couple times over the course of about 2-3 days and haven't had problems since.

PS- I rinsed my hydroton thoroughly before using. Be sure to do the same otherwise you'll get a bunch of gunk in your buckets.

Sorry it took so long for me to get back. I been out of it for a few days. Thx for the reply. I rinsed my hydroton before but clearly not enough cuz I still got some gunk. I change all the water in my DWC because i got a pH and PPM meter the other day and I checked my water. I had pH levels at 3.5-4.0!!! And my PPM was 1200-1500. I refilled the containers with pH 6.3 and PPM 400-500. Hopefully my plants will do better now. Some of the bottom leaves look like they are dying now but it has been a day since the change. Think they will recover???

how did you make out i am facing a similar issue?

well after changing the water and adjusting it to proper pH and lowering the nutes i was using it seems to have really helped. my plants are looking so much better and thankfully i have had no losses, except for some of them really suffered from stunted growth. prob cuz they had nutrient lock from the horrible water conditions. what exactly are you experiencing Heads? maybe i can help further considering i just survived....lol