Coral Symbiosis Question

Hi guys,
I was wondering if any of you have experience with coral symbiosis and coral health? I have trouble coming up with factors other than their microbial communities that have helped them overcome obstacles like disease, ocean acidification and of course, increase in temp. in oceans.

Do you have any ideas as to what factors, perhaps within the corals' own immune system or other factors (as long as it's not their symbionts) that help corals maintain their health? (healthy as in, having a stable relationship with microbes, no disease, no loss of color etc.)

Been trying to find papers but most research has been done on the symbionts being the happy helper. Many thanks if you have any theories!