Sounds like too much heat rather than too much light...

Maybe 8 inches away would be good to start. If the seedlings start to stretch then it might be too far away, so move it a little closer,

If they become too bushy then move it away. You want o keep about 1 inch between each node. then you have the sweet spot regarding light distance.

Listen to your plants, they are always showing you something

Take Care

S.L.