Snails dieing,but only from one store.

I got my little snails at a local pet store seems very clean and everyone well taken care of,ALL 4 SNAILS I GOT FROM THAT STORE PARISHED,now the other store i got my canas from,witch the poor guys were so beat up shells cracked and very thin at the end and scratched also the seemed to have quite a bit of algee on there shells,THEY ARE ALIVE AND DOING GREAT,i do believe i will venture back there and buy the rest tonight or tomorow shhhh lets don't tell hubby,he'll find out later
I have put in the time into really learing how to care properly care for a snail,and learned a few new things about fish on the way,what is the prob?They said my water was fine.Why only there snails?Do you think it was poor care or bad luck?P.s My snails Skyler and Shredder's shells are lookin really good,healing well.They will be strong like bull
Heather

