bottom leaves are yellow

My bottom leaves have turned yellow and the tips are seem burned. Some other leaves are looking like they are headed in that direction. If anyone can give me any idea of whats going on that would be great.

i have the plant in a grow box that is covered in tin foil, im using 3 cfl bulbs, and i watered the plant earlier today the nutrients i used was Miracle Gro citrus and fruit( it was the only thing at home depot i saw with NPK i wanted) the NPK is 10-15-15 o yeah and the plant is its growing stage.

Im going to try to get some pics up in a few.
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What size container, how big are the plants?

if they are in veg they should be getting nutes high in N and less in P. have you checked the ph?

no im just watching it for the weekend for my friend but he told me he wanted to get something high in P n K and generally low in N so i just got what he told me

well thats fine but i think he was a little misinformed, during the veg/grow stage the plants need a high N fert, that yellowing is from a lack of N from the looks of it. and the ph is probably off locking out the nutes that you are adding. get a fert with a more balanced mix somthing in the 2-1-3 range for growing and then something like 1-2-1 for the flower stage.

yeah ill try that thanks man