Well, Nyquil is about 5 different medications. The ones most likely to produce mental status changes are the antihistamine part and the dextromethoraphan part. Don't double medications in the future and watch for possible problems with these. Along with his illnesses he has had a fever each and every time, ranging from 101 to 102.3. I fear he has a deeper problem.
Kids get raging fevers when sick.
It would be more worrisome if he didn't. Get him checked out to take care of your concern, but it's probably normal. Small red spots will start showing up on my chest as soon as my fever starts to break. Over the next day, the dots will merge into a solid sunburn like rash and gradually fade. As I get older, the minimum temperature at which a rash will develop has decreased.