Nitrogen overdose is a definite possibility with leaves looking like that but the fert is so weak that I'm not sure where it would have come from.
Yes, you can control vertical growth- bend over and tie down, since you're already at your height limit.
I see burns not from ferts but from physical contact wiht the bulb.
Either way you need a bigger pot. Better to do it now before the rootbound condition decreases your potential yield.