if its getting worse, i'd water with some hydrogen peroxide asap, if you're using the 3% stuff from the store, i'd add 20ml per gallon for the first couple of times, then down to 10 ml per gallon after that. if you've been using beneficial organisms, you need to get something like hydroguard and use that instead, double the recommended dose for the first time, then follow the directions after that.
which ever you use, do it NOW...while there are still roots to save