Top of plant yellowing and sagging

[Jonnyrotten]

I have 3 large plants in 5th week flower. The top 2 feet of one of them is turning yellow and sagging over. (plant on the right) All 3 are the same strain same nutes same everything but its only happening on one plant.....any ideas.

I was thinking about adding cal mag that I have not done on any plant. Reading it might be sulphur deficiency?

 

[Jonnyrotten]

Anyone?
also I just noticed the middle plant is showing the same signs and the plant on the left is deep green.
1:2:1 ferts
EC 1.8

 

[Beachwalker]

Don't know what it is but here's something very similar hope it helps

Fox Farm with Frebo

Sad day. I cut her just below the first dying branch yesterday and today the lower branches are still looking good. The branches were hollow?

www.thcfarmer.com