how often do you add nutes?
At full strength?

Do the leaves look healty? Any yellowing, spotting or discolouration?

I know you got inside and checked for light leaks with the door closed ....... but you said you leave it cracked 1" ....get back in there and leave it cracked 1" and see if you have light leaks. I'm willing to bet that is what is slowing things down. The light leak is causing the plant to go back to a veg state.

ME