The spots you are describing sound like the spots on some of my frogs, like the photo but much smaller. In which case, they are completly normal

Do you use a heat mat or lamp? Or both? Or none..? I don't know the normal climate this time of year where you're from, as I'd imagine its different to over here in England, I don't know if its warm enough to keep a tank with no extra heat source.. but anyway, I swear by under tank/ side tank heat mats.