whats wrong with my plant? help please?

I remain unconvinced by the rootbound argument. I have some evidence for this point of view of course...

For a start, go and have a look in the LED forum at the party cup competition. Judging by the plants in that thread it seems entirely possible to run a grow from seed to harvest in a small cup as long as you have a good feeding schedule. True, it is much more difficult to keep them healthy compared to a normal grow, but it is certainly possible. It will naturally limit your yield though, as it limits the size of the plant.

I'd also like to see what evidence people have for saying that rootbound plants will display chlorosis in the absence of other nute or pH issues?

i'd defo go for bigger pot size, a gd size pot and drainage system and re-look at your nutes, they look gd and you've done well dont waste all these wks of work over silly mistakes. google rootbound plants, loads of pics and articles explaining all this