My baby is sick! What’s this rash?

Yesterday morning my 4 month old woke up with a cough. Throughout the day she got progressively worse. She has a mild cough, sneezing, congested nose, red and watery eyes, and just a moment ago I noticed a rash. She doesn’t have a fever as of right now. Her pediatrician won’t be open until tomorrow morning but I’m gonna call first thing. Just wondering if I can get opinions and advice.

What could this rash be? Seems to be the worst around her nipples. 🤔

Update: Checked her temperature again and it’s at 99.9 so I gave her some Tylenol to bring it down. Gonna keep monitoring it. ☹️