Re: stressed shubunkin
#2
Are you feeding them currently? If you do feed them during winter, then it's worth at least cutting back on the amount of food as the fish go into hibernation mode and their metabolism slows down - it may be that the food is not being properly digested and is affecting the swimbladder. If you do feed them, then I'd suggest, as well as cutting down on the food, interspersing flake/dried food with some peas with the shell off - that might help.
Let us know if this works or not and, if not, we'll try to advise further.