HELP! What is going on?

[atmabhoda]

I'm growing in rockwool and geolite inside, with the poor through-individual plant per tub method. Been doing this for years. beginning this past winter, the plants begin getting a white film on lower stem, then the stem gets a brown sore, maybe with swelling, eventually losing stem material. The lower leaves begin yellowing, eventually taking down entire plant. Roots are white-but plant eventually dies as the leaves yellow all the way up. Using dynagrow and hydro guard, teaspoon per gallon. Some plants survive, most don't. Been using this method for years-all of a sudden the plants are dying. What is happening?

[DoctorJohnson]

the plants begin getting a white film on lower stem, then the stem gets a brown sore...

That sounds like a bacterial or fungal infection. Pythium is the usual suspect.

Rock wool tends to hold an awful lot of water so maybe if you get rid of that it would help? (Soaking wet media and plant tissue are asking for trouble.) Rock wool is nasty stuff anyway--bad to breath the dust--and there are better, more modern culture methods.

Just my .02 as a grower microbiologist. Good luck!