plants leaves turning yellow and falling off 4th week of flower

I have tryed to compare the leaves to a defecency chart maybe nitrogen defeciency or maybee root bound im attaching picks need help identafying the problem an how to fix it. Hope its not to late. Any help would be greatly appreciated.
I have read for hours an have a few ideas but not sure what the problem is or how to fix. i have attached some pics

Seems a bit early, but it's normal for plants to shed their leaves as they approach the end of thier run. It's just 're-distributing' the nutes to the buds. Some extra feeding might help, but watch out for nute burn.

Definitely nitrogen defeciency. This is very common for beginners. What type of soil n nutes r u using?

If using miracle grow potting soil this is why. By this stage it's very low nitrogen. Add a small dose of high nitrogen fert to stop progression from getting any worse. (Note most of the leaves already yellow will still stay yellow but not a big deal As long as u nip it in the but now)

If organic mix like ocean forest or happy frog I would just top off with more soil (they tend too b nitrogen heavy) n feed very low dose of grow nute just to stop progression.

Some plants will turn yellow faster than others. You will definitely start seeing die off around now, but if it only a few fans, and the rest of your leaves look good, I wouldn't worry too much about it.