this may almost sound a bit slow...
but...
look at the shape of the sides of what you're calling "chunks missing".
Do the two sides roughly match up?
I had this kind of thing when my night temps went real low and I was over watering the girls..
they'd shrivel up a little claw like with the lights off and the temps in the low 40's, and when the lights came on, they'd almost POUNCE at the light and end up around the 75-80 mark.
It may have been my imagination, lack of experience, and maybe just a bit of general full of sh!tness... but these leaves seemed like they were tearing with the stretch.
Had nothing to do with PH and temps in the end.. but then again I'm an organic/soil boy so my 2c may be worth nought.
Good Luck
JJ