the lower growth is growing but the leaves are a little yellow. whats up with that?

u probably need more nitrogen

how old is your plant?

it is about 2 months. i always have fresh air comin in too. so what could it be. i use top of the line growing products?

if it just the lower leaves it could be nature, they die off as the plant grows,

if it more than just the bottom leaves (like the entire lower 1/3 of the plant) it may be telling you it needs something. This is highly unlikely as you said you are useing good nutes, I would not look for a nute def.