Conditions Advice on breathing with squeaking (& also hair loss)

[Kaybe4]

We are relatively new Guinea pig owners and after looking for a breeder/rescue near by with no success we purchased one from Petco. The day after I noticed a circle on her head of hair loss and took her back concerned for ring worm. They said they thought it was mites and would treat her. (That was on Wednesday) the following Monday they called and said she was better and ready to pick up. I was very skeptical after reading up on mites but I repurchased her even though the spot seemed bigger and brought her back home to watch and see. You?ll be able to see it on her head in the video. My concern now also is the way she is squeaking seems like she can?t get enough air. Almost like she is only getting air through one side of her nose. She is also a tiny little thing so it seems she is very young. I?m not sure if it something normal or not and would love for some advice. I want to make sure I'm not being paranoid but we do have another guinea pig and we haven't been able to introduce them for fear of spreading something.

Thanks for any advice

[video=youtube_share;alFpd06s43s]https://youtu.be/alFpd06s43s[/video]