She is 34 days old and I was watering her yesterday and noticed underneath the container there is a big crack. I could easily cut out the bottom and put into a bigger container to give more verticle grow space for the roots. Is this a good idea or could I damage my plant? I'm only taking the bottom out, not transplanting the entire plant
You could easily damage roots when cutting the bottom out. But thats not really a problem for mj. She'll grow new ones. And sure you can do what your planning. It just makes for an unstable pot and watering is a bit tougher to gauge. But no reason why it wouldnt work.
I did it to my plants (not auto-flowers) and it worked fine. You're bound to destroy some roots but they'll grow back fine.
Why not just transplant? And my first grow the afghan kush I completely mutilated the roots during a soil transplant and it still yielded me 3 quarters so no need to worry bout the roots.