Your seedling looks perfectly fine to me. When you do transplant, if you think the stem is too far, just plant it about an inch deeper.
Also I'd leave the light as-is. You should let the plant grow into the light if there's sufficient light, which 100 watts is way more than enough. Just go by the light manufacturers recommendation of distance for seedlings.
Also, most people only get deficiencies when they over-water and rot the root hairs. The rotting root hairs are why plants get a nutrient deficiency since the root hairs are rotted and can no longer uptake nutrients normally. A nutrient deficiency is almost never due to an actual lack of a nutrients. People over-watering then go on this downward spiral of trying to correct a nutrient deficiency, which none existed in the first place, and it was their overwatering that caused it all. Now that you know, you won't be 'that guy'.
Hope that helps.