I saw some vermitids a while back and broke them off. it hasn't rebounded though, only got worse. I have been thinking "quit touching it so it can heal". but sad hammer is sadder than it was.If it keeps jumping, you'll want to consider doing Something.
Broad Cipro is an option, medicated dips as well.
The "why is this happening" is always terrible. It could be a pathogen, pest, swing in parameters weeks to months ago...