Cichlidiot wrote:

As for the OP, check out fancy goldfish and see if any bear resemblance to
your mutated fellows. The described changes would be consistent with many
fancy goldfish forms. I've seen a few "common" goldfish for sale that
appear to actually be a cross to a fancy (body shape is off for a common
or comet)

And note that the original fish were "feeders", which could easily mean
culls from fancier forms - there's no telling what the source is.
--
derek