Re-gapping the spark plug is a good idea. I'll ty that tomorrow when it's not pouring rain. I'll look at the gaskets tonight. Would they just suddenly go bad? This is a pretty new engine so they're not old.
Could be a weak spot that just gave way. Probably made from old newspapers and goo.
Possibly the head has warped. This would be a good time to mill the head and top of cylinder if you have not already done so. There's some sticky threads covering this. Very simple to do.