Solay, Guess all of us are coming out of the woodwork. This must be a fairly common thing in that so many of us have it happening. I have a split leaf,too.
For some unknown reason, my oldest phal (which is also branched and has about fifteen huge,white, flowers) suddenly developed a split. I don't think it was physically damaged. I almost think Brookn is on the right track
...judging from the looks of your plant and the health of mine, it's almost like they grew too fast
