Hey guys! Any idea of what this could be?

Rio had diarrhea for a day and a couple days later had a fever for 2 days and didn’t sleep at all. Last night he slept realllly well. Now he has a rash. He is also getting his last molars and had a reallllly red ingrown toenail during the fever days but now it’s practically back to normal... 🤔

✨UPDATE✨

This is his back now! About a couple hrs after the other pics were taken. His back is now worse and it’s now raised....