I'll bring her to the doctor tomorrow, just in case. The odd thing is that over 3 days the original spots haven't changed at all. The skin around all the spots is perfectly normal (not red or anything). The sand fleas would make most sense as they seem like small mosquito bites. But the fact they are starting after we get home, and seem to be multiplying makes me a bit doubtful this could be. The lack of fever makes me doubt it could be most illnesses as well. but, perhaps she is just presenting something differently and therefore confusing me so I will bring her in to see. She is full of energy and happy as can be it's just these spots on her back/bum/thighs.