Markmahlum sorry to hear about your plants. What exactly is rotting on the plants? The roots or the base of the plant above the root line turning the leaves brown?

The base of the stem is rotting.

Thanks,
Mark

Sounds like a fungus conditioning because of the cross contamination (if that's what it is), but without pictures and probably more info it's hard to say anything. if the base of the stem is rotting that would be a form of stem rot. Usually due to water levels being too high. But the water is just a catalyst to all the types of fungus, bacteria and pathogens that can affect the plant. Some plants more than others.

I can go through a list of possible fixes, but nothing will guarantee it. Most will damage the plants if your not careful. How big are the plants? How many are you talking about? How difficult would it be to clean and sanitize the entire system, as well as replace the plants?

None of witch would do any good unless you know the cause of the infection in the first place. Is it soil born? Is it air born? Is it water born? Is it insect born? Unless you fix the initial problem it will just re-accrue.

Have you tried a week or two of PYTHoff ? I have had good results from stuff...