I ordered two pairs of wheels late last year. Due to a bad bike injury early this year I wasn't able to start riding until April. I built up my Time ADHX and have been riding with the first pair of wheels with no problem.
I decided to put gravel tires on the second set (ordered assymetric) and am around two weeks (three rides) into riding them. Last night I heard a loud bang, I thought it was the tire seating itself. To my surprised I saw a spoke had come off the rim. When I went to move the bike another two gave a loud pop and came off as well. Upon inspection, it looks like it cracked at the nipple.
I've never heard of such thing happening, let alone experiencing this on any bike. Any one have any ideas as to why/how this happened?

My tires were inflated to 45 psi.