well the temp where i am got as low as 10-17 degrees for a couple of days and nights i am in my 6 week of flowering, first timer i didnt have a heater in the room and my timer had died so light was off for how long i dont know (homemade flood and drain 18 gallon resevoir and a 5 gallon bubbler)...
i had the same problem use the h202 with the hygrozyme $36.95L it breaks down the rotten roots and the plant feeds off of them
i now just add hygrozyme to all my solutions its amazing
use the h202 2 tablespoons per gallon use hygrozyme as 1 tbsp per gallon
4 days change water dont use...