I'm going to be the alarmist jerk here:
Everyone else is saying COVID, because that's all anyone has on their mind when anyone is sick with anything now.
But I'm going to point out that ALL of these symptoms align with kidney disease. Rashes are HUGELY common in CKD.
Symptoms of kidney disease:
Fatigue (failing kidneys make less EPO, which means fewer red blood cells carting oxygen to the brain, causing fatigue)
Fever/chills (anemia and inflammation)
Nausea/vomiting (build up of waste in the bloodstream)
Body aches (build up of waste in the bloodstream, as well as electrolyte imbalances)
Blood in urine (self-explanatory)
Rashes (can be caused by uremic frost - when urea has built up to the point it comes out in sweat and irritates the skin)
Absence of localized pain in the kidneys (the most common causes of kidney disease don't cause any pain)
All of these symptoms can also fluctuate if the kidneys haven't totally failed.
You asked if anyone has come across this before and that you were "looking for ideas." My dad had all of these symptoms intermittently for several years as his kidney disease progressed. So yes. I have come across these symptoms before. There's my idea. Take it or leave it.