Its spreading...help!!!!

The top leaves of my plants are begining to turn yellow. I am on day 26 of veg. I picked off most of the yellow leaves from the bottom part of my plants(like I was told), but now I have some top ones that are yellow at the tips. What could this be?? I give REP to all who respond!!!! Thanks!!

u using nutes? u watering alot? temperature? lights? could be a few things tell us about ur set out

I am growing 9 white russian plants under 400watt hps. This is a soil growand I am using foxfarms ocean forest soil. My temp is at 80 degrees and my humidity is at 30 % (I know its low). About day 10 I added small dose of nutes. 16 days later the bottom leaves of my plants became yellow. I flushed the plants and all was going well. I repotted the plants 5 days ago. Now the top leaves are becoming yellow. I am not going to add nute again until I start flowering in about 6-7 days.

Check this out.
Cannabis Nutrient and Deficiency Table

Yeah good info...really helped out.