is my bird alright?

okay so this is probably nothing but I love my bird so much I just wanna make sure he is okay. alright so he is a cockatiel named bananas, and I just came back from march break and picked him up at the house of the girl that I leave him with for vacation. she’s very nice and good with birds so I do not blame any of this on her. when I picked him up I noticed that on both of his feet on the bottom of his longest toe the skin looked blistered and somewhat purple. he was also making strange noises that he hadn’t made before that are hard to describe but were very soft and kind of sounded like a crow. he was in a room with at least four other birds. one of the birds had been found outside(the girl was taking care of him) and had what appeared to be frostbite on one of his whole feet and was beginning to chew it of(my father is a doctor and said that the foot was dead and it didn’t hurt:in fact it will probably just fall off anyways”) okay so the blisters on my birds feet have similar coloring to what the soon to be one footed birds looked like. I know im being paranoid I just want to make sure. and you have any idea why his feet could have been blistered please post. thanks!