H orientalis doest get very big, at all, around 4" max. for females, and males are even smaller. Mealworms are completely inadequate for a staple diet for newts, they aren't very good nutritionally, they have hard exoskeletons that make them difficult to digest and they can bite the newts given the chance.
A staple diet should consist of either chopped or small whole earthworm/nightcrawler or a high quality pellet. Newts usually will prefer worms over pellets, but a lot of them will take both. And red wigglers are often refused because of a distasteful secretion they well, secrete, when they're cut.
If you still can't get them to eat after that, you might wanna try waxworms to entice them into eating again. Fixing your housing might also help their stress go down, and if you're ever thinking about buying more newts, don't buy from some petshop and wait until you get everything sorted out too.