Sorry for your troubles. Make sure you keep the new birds separate from your existing birds for a month if possible. You should use permethrin liquid or powder form to treat the birds and change all bedding. Repeat treatment in one week. Make sure the lice/mites are gone before you integrate into your flock. Easiest to see them around the vents and under wings. Give them a good quality chick starter/grower and they should do well. The smelly poop can be from whatever food they were getting. Many threads here on the forum with specific info on all your concerns. These birds sound like they are lucky you bought them.Post photos of them again in a few weeks, if you are so inclined.
