My 9 yr. old daughter has a rash on her trunk, and on one foot. We took her to urgent care and they tested her positive with strep throat (no fever or sore throat). They took blood work and found her white blood cell count was 2.8. They were concerned and asked me to have it tested again tomorrow. We just came back from Six Flags yesterday (water rides and roller coasters). Perhaps she picked up a bacterial infection? Or a tick that went unnoticed. I don t know where to start researching.
Without seeing the rash it is difficult to determine how it fits into this picture but a WBC of 2.8 is certainly low and inconsistent with strep.  A low WBC can occur with viral illness, a much more likely situation than other possibilities for low count in her age group.  The combination low WBC and rash suggests viral infection.  A much more remote possibility is early leukemia which should be identified quickly as it can be readily treated.  Autoimmune disorders can also cause a low WBC but this, too, is far less likely at her age.  My recommendation is that you have her primary care doctor see her tomorrow, consider rechecking the blood work with a bit more detail, and follow his or her advice regarding continued monitoring until the counts return to normal vs more in depth investigation.