Normal in my opinion from stress. Would also explain them coming "off" the food. Did you add any dechlorinator, vitamin C, or start right to the city water?
Vitamin C tablets, crushed between two spoons till pulverized and dissolved in pond water....slowly added to water supply aids in both stress but also counteracting chlorine/chloramines. I am sure someone out there will challenge this. But I have had success with both ornamentals, marine, and edible fish without trouble. I put 4, 800 millagram tablets in per 3,000 gallons in pond. And inside systems I use 1/2 a tablet for every 100 gallons.
I don't dose this regularly, only when I have a crisis. I am not sure what the max tolerance is, or how long it stay suspended in system. But this is what I do as a "home remedy" and it gives me good results.