G.D.
I'm not sure if the grandparents are on which side but someone needs to put their foot down and tell them to back off. YOU are the parents and unless you go to them for advice it would be great if they kept out of it and let you and the DR's handle the situation. Making boundaries is only going to help the situation. I will tell you right now what the problem is mostly likely! MOLD! You need someone to come in and do whatever construction is needed and to do it RIGHT the first time. I'm no sure if you've seen the show on DiscoveryHome or DIY where they come in, find the problem, and trace it back to the cause of the issue. Remove the problem and fix it right beyond any minimum code requirements. That sounds like what you need. But you still need to enforce the boundaries with the grandparents. My FIL has even tried to convince us to allow my son to live with them because he has issues in school! Yeah Right! They allowed my DH to drop out when he had issues! Set the boundaries and enforce them.