Sorry to hear about the problem!
Thought about getting some aeration going? That is something you can do this year still.
I think I would get a water sample tested. FHM can survive in really bad water. Since yours died, IMHO I would try to figure out the reason before I started stocking any expensive fish.
Hopefully, one of the pros will be along to offer you some opinions on how to proceed.
Good Luck!
Last edited by Bill D.; 08/24/16 08:56 PM. Reason: Clarification