Were you the first person in line to use the facility? If so, I suspect it may have been Iron bacteria that had settled in the lines during non use period. The parks in Michigan have just recently opened and most likly have not seen much use because the weather has been so chilly and wet. I always run the water from the hydrant on the ground for a few seconds to clear out any settled "stuff" before hooking up or filling my tanks. Not saying that is what happened to you but sounds like it is a possiblity.
By the way, have camped at that campground several times and never had a problem with the water. Perhaps something has changed, since it has been a while since we were there. It is not too far from where we live.
Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine