Red itchy rash that turned dark no other symptoms but fatigue have been on him for 2 weeks now wbc was high could this be mold realted?

Tick-Born Illness?: I will presume that 'on him' should read 'on abx' for 2 weeks. It sounds as though the treating clinician may have suspected a tick-born source of your rash in the setting of fatigue and prescribed a prolonged course of antibiotics to treat. Mold allergy (any allergy) can cause a variety of symptoms, including rash, but treatment for mold would not require antibiotics.