It's normal for the 'seed leaves' or cotyledons to die off once they've been spent. If the true leaves start yellowing there would be a reason for concern.

Thank u...I believe that is what it is...I appreciate the response.....the guy at the nursery shop yesterday said it was cause they're getting to much water, I read on the Internet to make sure they get plenty of water and sun....there's only a few trees in our subdivision and we don't have one..I water em everyday for like 5 min and that's it..any truth to what he said that u know of?

If your soil drains well you shouldn't have any problems. Too much water in poorly draining soil can rot roots and leaves will start yellowing as the plant dies. If the plant looks healthy and just the cotyledons drop, that's normal. Also, older bottoms leaves will die off as the plant matures and that's normal too. If new young leaves start to yellow, I would look at too much water or not enough nutrients...or both. HTH

Ok...thanx....looks like I got nothing to worry about then...its maturing and the new leaves are very green and healthy looking...so looks like I'm ok then