Soo sad, it must be heart breaking i can't believe they haven't found the cause of it. It is not your fault it has just happened even tho these animal's have passed they knew a loving home and now have someone to wait for at the bridge. Please don't give up, take some time by all mean's and maybe start slowly, Bleach and disinfect the house's and cage's leave them to soak in it if you can then store them til your ready and do it again before use, there are not enough people who can do what you do, your heart is breaking now because you care so much but if you didn't care you wouldnt be any good at it. we need more people out there like you not less!