Yellowing top leaves

[John6369]

This just started happening over the last 2 days.

 

[Rwise]

Check these out from the Pant Problems link above. Whats the PH?
https://www.growweedeasy.com/cannabis-plant-problems/iron-deficiency
https://www.growweedeasy.com/cannabis-plant-problems/zinc-deficiency

 

[dirtymike]

Big plant in a small pot. PH is probably off and cal- mag is gone. Rwise pointed out a reference that I have used many time's. It's a informative read.