Help! What could this be?

My 5 year old daughter has had these bumps under her arm for two weeks now. I first noticed them after her beach birthday party. She took a shower the same day and they were there, I thought it was maybe a rash from the water or sun. she was with me for a few more days after then went with dad for a week and now that she’s back with me they are still there and I’m getting more concerned. Her primary pediatrician has left office and we are in the middle of switching pediatricians so I haven’t set any appointments yet. Any ideas as to what this could be??? They are just under this arm but the other one looks like it’s forming like two bumps