Anubias Massacre

I bought several visibly healthy anubias nana/anubias nana petite from Petco a few weeks ago, and they seem to have been doing pretty okay (one of them even appeared to be growing new leaves), until today, my latest water change, where it appeared that almost every one of them had started to rot. My other plants in the tank, java fern and marimos, appeared totally unaffected. I inspected the roots and they were soft, brown, and slightly transparent near the base of the plant. The leaf stems were slightly yellow/transparent as well. Several of the leaves fell off on their own, and the plants emitted a rather nasty smell. Needless to say, I did an impromptu operation on all the affected plants and sliced off every unsalvageable leaf at the rhizome. The remaining leaves appear in decent health, so I'm hoping they make it out okay. Does anyone know what could have caused this/what course of action I should take from here? I thought anubias was practically unkillable. The beginnings of new leaves I saw growing gave me a lot of hope, and I thought they were doing well until they weren't.

 

lighting? perhaps something at the store is different from your water and they are rotting and regrowing so they adjust? Did you buy the rhizomes?

 

Did you burry the rhizomes? If so then that's probably what killed them.

 

And even if they were not burried: I had a case lately, where I cut a big Anubias into smaller pieces and one of the pieces had direct contact to a part of the driftwood with a lot of biofilm. It was like the rot from the wood took over the rhizome. Affected just one of 5 pieces, though.

 

Make sure you dont leave any rot on the rhizome as it will spread

 

Did you buy them tissue cultured or submersed?