While prepping for the new season I found cracks on both front K1s (2 on left one, 1 on right, all on inside lip). ~40 track days on these, about half with current tires. Rears are both fine.
I check wheels before every event, this is definitely a new development. The only scenario I can think off for the cracks was a very rough transition between infield and banked straights on my last event. There was an actual gap of a few inches upsetting balance on every transition.
Check your wheels, better safe than sorry!