Definitely do the heartworm prevention for all the pups. I did read that the medication could be why her liver enzymes were elevated in May. They weren't a concern at that time though.
The vet said he's checking for thyroid issues and if not, we'll check for Cushings. I don't know what her quality of life would be with Cushings, still researching that. I won't let her suffer but based on her current condition she's happy and active. We're feeding her a third meal for now to keep weight on until we know what's up.
What is Cushings IM (sorry to ask but I'm at work and can't do the research at the moment)?