Yes you are probably overwatering. Miracle grow potting soil is mostly peat and peat holds the water. I don't like peat pots either. They would have to be peeled off the plant before you plant because they do not decompose like they are supposed to do. They also retain too much water

Once a plant has germinated they don't have to be kept moist like they were when they were germinating. In fact keeping them wet is a sure way to invite trouble. Wait until they dry out a bit and then bottom water. Wait until they dry out at LEAST half way and then bottom water. When you water depends on the size of the plant and the size of the pot. A pot needing water will be light. You'll see how much heavier it is after you water.

To bottom water--set the pots in a shallow dish that has water in it. Wait until the soil darkens a bit on top. Then remove the pots and let the excess water drip out. Now your plants are thououghly watered and can wait a good while before you do it again.

Letting a plant dry encourages the roots to go deep in search of moisture, so you have a better root system and a healthier plant. Over watered plants are weak and have a poor root system, not to mention inviting diseases like damp off and root rot to set in.

Thank you for your help. I will try again with my leftover seeds and be more careful.