Hey Pal!
Don't scrap it unless they are toast. My res never got below 24c (75f) and averaged 77-82F every day. No funk, no fungus. I used Dutch Master Zone at the aggressive rate and peroxided the hydroton about once a month. Just squirted it under the plant, let it set a few minutes, then flushed it into the res with RO water. Not one speck of fungus and the bucket was root packed. Cleaning the bucket was not going to happen with that plant for the last 2 months, so I just kept it dosed and bubbled the hell out of it to keep it aerated.
You CAN grow DWC in higher res temps with the appropriate precautions and good oxygenation!
Fish