Does anyone know any ways to prevent root rot? My reservoir temp is 72 degrees and the plants are in 4 inch rockwool cubes. I have been in veg for 8 or 10 days. There is pythium in the reservoir. It builds up around the edges and around the fill and drain tubes. Any advice would be greatly appreciated.

Horticultural grade Hydrogen Peroxide. That and cooling your resevoir.

Most Hydro shops sell that type of 35%hydrogen peroxide. I use a tablespoon every time I top off my res.