yellow leaves up top

[dairyman74389]

i have a couple yellow leaves on the top of my plant....they are about a onth in veg and in foxfarm soil. temp satys at about 80 and humidity at about 70. its only 2 of the top leaves which are yellow...the rest look good. why are they yellow? any ideas to fix the problem?

 

[pcduck]

Need way more information, but....How close are your lights? and what type are you using?