Would it be bad to just leave them both in 24/7 until they're both a bit stronger? Since they're ponies it seems like the stall would be pretty spacious to live in. I know nothing about rehabbing horses or ponies in general though, so take my question/suggestion with a grain of salt.

image"Avoid loud and aggressive persons, they are vexations to the spirit." - Desiderata, Max Ehrman. 1926. image