If the peels are not discoloured and are cooked, then the only concern would be dietary imbalance. The more potato peelings they eat, the less formulated feed they will consume. Potatoes are high in carbohydrates and low in protein, so there is a risk of birds getting fat/obese if it is more than 5-10% of their daily intake on a regular basis. If you offer them a higher protein feed rather than just 16% protein layer feed then that may offset some of the concerns but you would still need to limit the amount of potato you were giving them, in the same way that scratch needs to be limited, especially if you are emotionally invested in your birds and would be upset if they got sick and died. I am aware that sounds over dramitic but too much carbohydrate in the diet can lead to a multitude of quite serious and even fatal ailments including Fatty Liver Haemorrhagic Syndrome, ascites, egg binding and prolapse, salpingitis and internal laying. Some people raise chickens to produce eggs and that is their sole purpose. Most people here on BYC have at least some emotional investment in their birds, so it is worth understanding the risks of deviating from a formulated feed.
Layer feed is formulated to be a complete feed that supplies laying birds with all the nutrients they need to produce eggs and remain healthy. Once you add extras you start to tip that balance, particularly if they prefer the treats to the layer feed as is usually the case. That minor imbalance over a few days or even a week or two is not a problem, but longer term is when issues start to arise and sometimes you may never know that things are not as they should be until a bird dies suddenly from Fatty Liver or prolapses. Obese birds are much harder to notice than other animals because those feathers hide it so well.
