What is this crazy red-non itchy and bumpy rash?!?

Okay, I run a daycare and I have had the same kids for over a year. Two of the boys I care for developed a very small one day fever and then it disappeared with no symptoms other than loss of appetite. Then, my son developed a small fever that lasted 3 days. Now one of the little girls I care for developed a fever. For some odd reason my son and the little girl both got this odd rash all over their body. It is a whole bunch of tiny red dots that are non itchy. We thought it may be heat rash..but I cannot find many pictures that resemble our childrens skin. There have been no changes in cleaning products, detergents, and no medications either. Has anyone experienced this before or know of any place where I can get some answers? Thanks!