should i go to vet

Hello, I took my cockatiel out of her cage this morning and found that her feathers had a strange color right under her wings. Is this something to be concerned about?

I actually just created this account today because of this. Apollo is a one year old conure and my second bird. Recently I’ve noticed a small patch on his chest that I could see his skin from. Immediately this sparked alarm, and that alarm only grew when a week later the patch seemed to grow...