How close is the your light?
How strong is your feed?
Looks like most tops to the left are generally green?
Whereas the tops toward the centre of your tent are yellowing?
What is your light source?
Canopy temps?
Tbh i think it could do with some plain water as well.
Ph of your media?
Ppm of your feed? How often?
What type of medium?
Watering how often?
Could be a few things.
It doesnt immediately look like iron deficiency.
Looks either under, or over nuted/salty.
Or ph issues.
Or both.
Need more information.