If you see no aggression (and you're watching from a distance too) I would keep them in QT if it was me. I might try a divider or a larger tub if you're still concerned about them.
I guess they could not be eating bc they are not used to the tank and still stressed from shipment or not enough space to feel comfy. But I def wouldn't add fish that are not eating to the main tank. I'd use a tote bin before I put them with my own fish.
Also i'd change water at least every other day for QT. And I feed Metro and esalts for 3 days.
About QT, some ppl treat Prazi as prophylaxis. Same with Metro against potential Hex. Personally I watch and wait to use Prazi (mainly cuz I can't get it here) and just feed Esalts against Hex. But I deworm all new fish in QT after I was burned in 2017.
So prazi against cestodes and trematodes
Metro and Esalts against Hex
Dewormer for nematodes