What do I do?

Hi everyone, I have 3 ferrets that I love dearly but noticed they have been itching, sneezing, and sleeping more. A day after that started we had found black mold in our house (I live with my parents in the in-law suite). My step-dad owns the house and isn't actively trying to fix the mold issue so it's not like that will be done anytime soon.

Is there anything I can do to help them? I keep air purifiers running in all rooms, mop/wipe down walls, and vacuum often. Or is the best outcome for them is to be taken to a shelter?
I would hate to get rid of them but if it's for their best interest I will to protect them.