I have never personally grown with hydroponics but I will apply basic science to this the best I can.

1) Do you expose the roots to air often and is the air being circulated fresh?

2) Do you use latex gloves or disinfect your hands before touching them? - wash for 60 seconds with warm to hot water and soap then put on gloves....

3) Is the water valve or the pump self feeding or hooked up to a line in your house?

Those are my best guesses. Unless the nute sources you drop from are slimy too.... :weedpoke: