Hmmmm clowns are just not as stable and hardy as most thought.... Hmmm next time, try to ask them to feed to see feeding response before buying... they just die suddenly for no reason at times... so at least if u know they are feeding at the shop and not at ur tank even after a few days, u know that its ur tank parameters/problems... do share ur parameters, size of tank and such for a better diagnosis like what most said...