You may have stumbled upon one of the other threads I've posted in on this question, but I don't mind repeating. Corydoras will shoal together as same of different species. I have found that some do have a distinct preference for their own species, moreso that some other species have. C. panda is one of these; they definitely prefer to be together if given the option. For this reason, I always suggest three as a minimum number for any one species of cory when you want more than one species. Fish that are able to be in a more natural setting with respect to their companions and such will always be more relaxed and thus in better health.
You're right on the panda health. Given that this species is now mainly commercially raised, they are very sensitive to water parameters, water quality, temperature and environment. They will always settle in better in an established tank with stable water qulaity and parameters, and at a cooler or normal temperature; 78F is their upper limit long-term, and they do well in the low to mid-70's. Most of the Corydoras species are better suited to lower temperatures, by which I mean up to 78/79F. Some do fine higher, C. sterbai comes to mind, and is often chosen for Discus
aquaria with temperatures in the low 80's. The pandas would "melt" in that.
And, last but certainly not least, welcome to the forum. We're glad to have you.