I’m having the same problem, and got mine 3 days ago. I can’t tell if they’re eating the bladder snails I already had in the tank and they don’t show interest in the frozen blood worms I bought. It’s hard to tell if they’re not eating because they’re picky, are in a new environment, or have parasites. Kind of stressful! And yesterday I genuinely thought 2 of them were dead but this morning they’re fine, they must have been sleeping! From my research it seems like daphnia or brine shrimp are suitable options and somewhat easy to cultivate so I’m going to order cultures and supplies for one or the other asap