From my understanding of bloom it will probably be a light crystaline grey/white powder coating most of the cigar exposed to air (So not whats resting on the cedar), not just certain spots on it.
Certain spots of white fluff or other non-crystaline looking growths will probably be mold. It'll also look more "3D" than ploom/bloom will, and probably have spots of green, blue, and yellow.
Check your humidity and if you perhaps have "hot-spots" of moisture getting trapped in areas of the humidor, which could cause mold when the hygrometer reads normal. Good airflow and not overfilling the humidor will allow a evening of the humidity, and that will help with keeping random mold from popping up.