1. Pics would very much help in figuring out what's going on here. If you're flushing already - you may be burning them a bit on top of overwatering, because those "time released" ferts dissolve in water!
2. I also use Scott's premium Potting Soil - you should be fine with it.
3.The lights you have are great for a new seedling, especially as they are sensitive for the first couple of weeks. After that point, however, you want a minimum of 3000 lumens per square foot of growing space, 5000 lumens per square foot recommended. So you'll need to come up with a better lighting scheme for them.
Leave your fan on 24/7 - don't shut it off with the lights. Don't have it blow directly on them - you want to set it so it makes them shiver. This serves the dual purpose of helping them with air exchange, and helping the stems grow strong.
As for nutes - as I said, I use the same soil as you, and thus far I've had great results in veg, with MG All Purpose Plant Food (liquid, in a yellow bottle) at one teaspoon every other watering, one drop of Superthrive per gallon of water every other watering, and one TBSP molassas every other watering.
Hope all this helps, good luck with your grow!