After much reading it looks to me like my cats have proliferative Gill disease for which there is no treatment. The good part is it only effects channel cats. The bad part is I loved my channel cats. I’m guessing it was present in some fish I stocked last year. I’m bummed but hopefully some will survive. I guess it’s a common problem with farm raised channels. If anyone has any info on this please chime in. I can’t seem to determine whether this goes away with no host species or if it remains in a pond indefinitely.