Need some help!!

Hi there, hope everyone is doing well. Been awhile since my last grow and am needing some expert eyes and advice. Have noticed some light green at the top and not sure as to why.
Set up:
#7 pots
Bubba Kush (about 6 weeks)
Hollands secret 3 part
Additives: calnesium, super B+, Royal gold, propogator and carbo blast.
Sun system 630LEC (29”above canopy)
Temps 73
C02 at 1200ppm
Humidity at 50%
No yellowing or signs of deficiency at the bottom or middle. Not sure if it is a deficiency, PH problem or something else. Any help is much appreciated.

 

It is Sun system 630 LEC AND 29” from canopy. Not sure on the lumens or PAR.

 

I was thinking that it might be iron deficiency I was just trying to see if there were any others that saw that before I spoke. Haha thanks so much. Flush time it is.

 

Thank you so much for the info, extremely helpful.