I would not add any cutrine or other herbicides now especially if the fish are stressed. Cutrine is copper which is fairly toxic to everything. I would also check what you normally add for dosage and make sure you are not overdoing it. I am sure it was just a rough winter that caused the kill, but I would lay off the Cutrine until they get better or you re-stock to be safe.
My uncle's pond in NJ had a fish kill 5 years ago. Killed many fish. There were many bluegill killed but some did survive. However, all bass were killed. We waited for a year before restocking thinking some were left and would reproduce, but never saw any and the thousands of happy frogs around the edge and jumping in with no fear confirmed no bass!! We did restock some bass from another pond and everything is happy again. Even though a fish kill is not fun, it is actually fun to re-stock and track populations, etc.
