A small frozen watter bottle in your rez will drop the temp and stop root rot. that is common when the water temperature gets to warm but just a bottle or two frozed and droped in is the key.

I have been know to make up extra nutrients and then freezes it in ice cube trays to bring down the temp of a rez in the summer. When they melt you get new nutrients. The water was Ph balanced at the time it was covered and frozen so its fine to drop in your rez if you have temperature problems.

Just an idea that may help.