Seedlings can only have 3 problems, Moisture, soil, or light. You should not be using any fertlizer, seedlings dont need it.With an intense light like you have, it should be as far as it needs to be away so as not to cause signifigant heat build up. 1.5-3 feet with a fan on the glass.
The soil medium could be bad, anything with too much nutrition can burn seedlings. Im not saying thats your problem. could you mention your medium again?
I think you have a watering or heat issue, which is what causes my seedlings to bend and flex. Its possible that your watering too much/not enough. In those cups you should only need to moisten the soil every other day. Add water slowly till water begins to drop through the bottom, thats when I stop and wait another day. You need to get a feel for how dry the soil gets. I generally look at the top to see if the soil is very dry, then flip over the pot and look at the holes. If both are dry they need water.
How hot is it? Heat kills seedlings
Dont stir the soil with an incense stick, the inital roots are very delicate. Every week or so consider poking holes in the soil before and after you water to airate the soil. Stab, dont stir.
in vegitation...
