bottom leaves yellowing

on every one of my plants the bottom leaves are yelow or turning yellow , the top of the plants are doing great tho , any ideas ?

Fan leaves on the bottoms of plants die regardless of health. Sometimes they just can't get enough light because the top of the plant is blocking it. The plants look pretty good, really.

Looks like they need some water.

I agree with above, top canopy will block light and thus kill off the leaves it is not using. If the plant isn't getting anything from the leaves since they cannot get light, no sense in the plant continuing to keep them fed. Just normal process.

or it could mean they need more nitrogen also..

wow i was happy rite up until that last comment lol , now im thinking there not getting fed rite.

Looks like Natural Selection.. The plant has decided it is gaining nothing from the leaves and is disposing of them. Remove them and if the problem does not continue then you are in the clear.

P.S if it is a Nitrogen deficiency then the top leaves are normally the 1st to show signs as the older leaves store it from when it was around, but the newer growth have never had access to it, so they are deficient from the get-go..

ah k it makes sence , im using cfls... ill trim them off and see what happens ,cheers.