Yes than can change back once conditions have improved. For a positive ID, post us some pics and we may be able to help you out.
If they are kuda you are looking at, IMHO, a 65 gallon tank at least to keep them all long term.
As far as saving them all from the LFS, and most of us have been there ourselves, you are just giving the store reason to keep bringing more SH in when they have no clue how to care for them. It is all about supply and demand, if you keep buying them, then the LFS has the demand to keep supplying them. Sometimes, as hard as it may be, you have to leave them at the LFS. Once they lose enough money from not selling them hopefully they will quit buying them and bringing them in.