What you are seeing is not normal. It could be a water issue, or it could be stress, most likely place to start investigating is the water quality numbers. We always like to start with numbers for ammonia, nitrite, nitrate, KH, pH and temperature. Whether it is the cause, or if something else is the cause, the recovery needs to have excellent numbers. We prefer drop type tests or better as the dip strip tests are very temperamental, giving more wrong numbers than right numbers.
In addition it is always good to have information on the pond, like size, filtration, rocks or no rocks, age, number of fish, and when the last fish was introduced, and what kind of quarantine was used if any.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard