Wildlife rehabber, fawns with diarrhea

Hi all, I've been reading through posts and am so happy to find such great info. I'm hoping for some help with my fawns. I'm a regabber in Oregon, this year I have 12 fawns they are all weaned now and eating well. I have been battling with diarrhea with three of my babies for 3 weeks now, I have used safe guard liquid after fecal positive for strongyles, corrid after a positive fur Coccida and now they are still liquid diarrhea and still positive for strongyles, I was going to try ivermectin.. do you think that's appropriate or any other suggestions?
Also during this time these fawns have lost weight, would love some advice for weight gain without contributing to diarrhea... Any help us very much appreciated, they were going to be released in a couple weeks but that has been postponed due to this!!! They are currently eating calf manna pellets, antler max pellets, alfalfa, and I cut brush daily ( butter brush, wild rose, willow, ..) thanks again!!

You might interest the veterinarians at the university serving your area in your operation. They might have an Extension Veterinarian that could help.