how long did you
acclimate them? they are probably just adjusting to your new tank, generally when i get a new fish i don't feed them the first night or morning that i have them to give them some time to settle in. if yours don't look ill (keep an eye out for fin rot,
ICH, discoloration, etc) then they probably just need a little time to acclimate to their new surroundings

if they don't start to per up in a few days or a week then there could be something else wrong with them, but for now i'd just keep an eye on them and see how they do.