If they have developed more than 1 set of true leaves then they likely need food, especially if it is that long until you can plant them. Diluted 1/2 strength liquid works well.

If it is just the cotyledons that are yellowing then it is usually too much watering - a common problem with those peat things. The pots wick the water out of the soil making it appear to be dry and in need of water when it really isn't.

You'll find any number of discussions on yellowing leaves on tomatoes over on the Growing Tomatoes forum here.

Dave

calcium deficiency is my guess, but im no expert.

Here is a link that might be useful: robs urban farm

Thanks so much. They are pretty big so I think I'll get some food for them.

We've also had VERY wierd weather. Last week we had temps in the 90's all week, then the last few days it dropped back to normal (60's) and now the weather for the next 10 days is calling for 70's. I might get a chance to plant some early this year.