That happened to me. I had a big crash and everything on my rocks died. I found dead worms and all sorts of critters. Take them out if you see them. Just wait it out. The balance of life will take over. Mine took 5 weeks. After it was done spiking I added more LR
to help seed the rest of the rock that had "died". Don't get discouraged. I messed up and performed alot of PWC
during my spike which accidentally helped hinder the nitrifiying bacteria to grow into big numbers.