Day 48 leaves all going yellow

3rd grow my leaves have went yellow and falling out
Not that hung up on it like but any tips for keeping them green?
Cal mag I've heard of I have never used it
They have Been drinking loads of water lately too

Just add
I use 1ml per ltr of bio bizz grow
2 ml bio bloom
2 ml top max
Half ml pk 13 14 but finished using that
They are 10 weekers so I have 3 weeks left
Just plain. Water last 2 weeks that will be no leaves left I think
If its the same as last grow
They went yellow earlier last time
Maybe to do with not enough water maybe ?
Cause I gave them more water this time wasn't as drastic

Snapped a few branches to man
Don't know when the last one happened

What’s your temperature? Mine do that when I drop the temp and lower the humidity around week 8 into flowering.

To prevent yellowing fan leaves, up the dosage of N. Pretty straight forward. Not sure of it will make too much of a difference now, but keep that in mind for your next crop.
Its a common thing. Many growers lighten up on the Nitrogen dose a little too early.