First, do a good water change, that never hurts anything.
Do you have water test kits? Absolute must test kits are ammonia and nitrite... test for ammonia first and then nitrite, both should be at zero. Best test kits are the vial and dropper ones, not the test strips, which are notoriously inaccurate. Also, a pH test kit is cheap and good to have, and so is a nitrate test kit, though it's a tad more expensive than the others.
If your tank is cycled, I'd say give your loaches time and let them adjust. I imagine they are only a couple inches in length, and as you're planning on getting a 90 gallon, ten should be fine in your 50 for a good while.
How do they look? If they are plump, orange, and swimming energetically, they should be healthy. Also, when loaches are in packs, some gray out their black stripes as a sign of dominance or submission.
Sometimes mixing the food in fresh garlic juice stimulates appetite.