What is the water parameter they were in? Beside the temperature. And how long the tank was set up? And what is their tankmate? And what kind of water were they kept in the shop?
I'm sure the additional info would help. But here is my personal experience. Although they generally do better in lower side of temperature if they are not born and raised in other water parameter. And they do not take sudden change well, either the ph or temperature or even the difference of the degree of the agedness of the water.
And they do better with highly oxygenated water with nice current. I use powerhead for that. And you see them enjoy swim in the current.
Also some of the store bought Pandas are not hardy, especially the one come from the mega store chains in U.S. Also the stores find them tough to keep and they discoutinued to carry them anymore around my area. After all those mega chain have one of those central filter system and all the fish kept in same water parameters. And I bet the Panda didn't do well in typical community water for long.
I keep mine in un-heated tank with good filters(over-filtered) with nice water movement. In winter, they drop to high 60'sF but now it is getting warmer around here I think they are around 78F. But I think they would do better in low 70'S generally. And they are still making eggs. So they are not too unhappy about the Summer weather, I guess. But like I mentioned, they do not like sudden change even something better for them in long run. Once friend of mine lower the water temperature too quick and she lost many fish.
To me, you should get the Pandas from somebody locally breeding if it is possible. If you are in Seattle, I could hook you up with some young Pandas. Check the local aquarium society, sometime some member is breeding them and have some healthy young for sale. Also you can ask him/her the detail of the tank set up and maintenance.
To me, they would be hardy enough once they settled and kept in the right tank. And they even breed easy but you just have to get them healthy fish. And preferably kept in their own tank with nice group.
Good luck. They are cute fish and they were my favorite and still are. They may need little more TLC than regular more hardier Corys but it is worth it.