if the rez is too hot put a small baggie of ice in there make sure to take it out withn a few hours and replace it. as for the watering, they look very young and i would rather put them on a 15 sec on 45-60 sec off that will keep the roots cool and oxygen enriched. as they get older increase on and off times to accommodate healthy looking fast growing plants. and the ph pen is defiantly a must! good luck dude

I let mine run 1 minute on and 5 off start to finish..

Peace

Myself on my tubes, If any open spots, I block them, so no light gets to the roots.

SeaOfGreen

Aha... Never thought of light leaks.. There's the voice of experience talkin... Just goes to show how much I have to learn.. Thanks, seabc!!!

That's root rot and it will spread to your other plants.
You can dry an h2o2 treatment, with perhaps some hydrothrive, or superthrive.
You need to reduce the water temperature.

The constant flow of water will heat the water above what your ambient rooms temp is.
If you see mold on the roots than you are not getting enough oxygen to your roots. It's too warm somewhere. That's for sure.
19celcius is 66farenheight so your rooms not warm enough either in my opinion.

I've added one more pump in the rez to mix the nutes and enrich water with o2.., they're both in water and running 24/24.. the bottom leaves are drying out and I see new white roots coming out.. I think it was because of the water, I changed it too late once (14 days).. now I'm changing it weekly.. my plants look revived.. I will try Superthrive as krimzon sugests and keep you informed..

I was abroad for couple of days, and asked a friend to watch them daily.. bad luck.. it seems there was electricity cuttings during the night.. I found them at 28C under lights, and about 24 in the room.. but temp memory shows there was max 30C and min 12C under those lights..

that's one bad shock for them and those white roots they were getting last week are all greyish/brown as the old ones.. i have some big interrest to know if there is hope for any buds from them!

I added a few drops of superthrive in the tank (about 40-50L of water) and 40ml of 3% h2o2 today.. now the temp is constant 24C, under 20C in the room..
any thoughts?

The best solution is a chiller, plain and simple.

Get yourself a good enzyme product on the meantime. I prefer cannzym or hygrozyme. They work great in combination too.