Can you post any new pictures of the feet? I would find out how to get a culture done on the pus or exudate coming from the foot lesions. Call your regular vet, your state poultry lab in Mass. and ask how one would go about that. Test for Mycoplasma synovitis and other bacteria. It shouldn’t cost that much. It can be dangerous just treating with one antibiotic then another, not knowing exactly what the problem is. MS according to Merck vet manual and others, say that MS is usually not easily treatable.
I would try to get a diagnosis before using more antibiotics. And I would give probiotics (probios powder) or plain Greek yogurt with live cultures while on antibiotics and for a week after. Give the probiotic in between doses of the antibiotic for best results. This can help prevent diarrhea and help to replace the benifical gut bacteria.
https://health.usnews.com/wellness/articles/getting-your-probiotic-fix-when-taking-antibiotics
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601687/
I would try to get a diagnosis before using more antibiotics. And I would give probiotics (probios powder) or plain Greek yogurt with live cultures while on antibiotics and for a week after. Give the probiotic in between doses of the antibiotic for best results. This can help prevent diarrhea and help to replace the benifical gut bacteria.
https://health.usnews.com/wellness/articles/getting-your-probiotic-fix-when-taking-antibiotics
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601687/