Bottom leaves yellowing just along edges?

Sorry, don't have any pics. I have a 1 month old plant that's about 6" tall with 7 pairs of leaves and some new growth at the internodes. The plant looks very healthy except that the bottom set of fan leaves are turning yellow along the edges and it seems to be moving inward. Only about 2-3mm or 1/16th of an inch along the edges has turned yellow but I want to fix whatever is wrong before it gets worse.

Jiffy Mix (80% peat moss, 20% perlite, less than 1% lime) in a 6 inch pot.

Terracycle plant food .03-.002-.02 once a week

Water every 2-3 days when soil drys out

Light CFL's top and sides 1-2 inches away

fan constantly blowing on plants

I just noticed the low amount of Phosphate in the Terracycle plant food. Could this be the problem?

Thanks.