What is this common discoloration during flowering?

I feel like I see this in a lot of grow diaries. Around week 6-7 of flowering, the leaves get burnt tips and turn yellow.

Is this a phosphorus burn or deficiency? (Not my pic)

The lower leaves are green so it's not N deficiency. I can't tell what these growers are doing to make their plants so yellow. Maybe burning the shit out of them?

Mag.
Fixed with PH flush or low MG fert