HPS lights too close will burn the plants. They are young and tender. I am not sure what watts or how far but much easier to burn with HPS.
Second point is for sure they need fertilizer. Problem is giving them fertilizer and asking them to grow immediately is not good. They need to soak up those nutrients and then give them more light but for now move away some. Don't take out but ease up on those lights a little.
Agree on feeding but disagree on HPS for seedlings but it can be done but you just be careful with exposure - getting too close.
My statement about HPS was not correct though and HPS lights generally work best for flowering but this 430 watt HPS works very well for both - I know I have used but started plants under florescent lights and slowly worked them into HPS much more lumens especially the bulb I used some 58,000 lumens for 430 watt HPS. This HPS light has more blue than most, nice bulb.
http://www.usa.lighting.philips.com/pwc_li/us_en/connect/tools_literature/downloads/p-2707b.pdf
MH lights work well for vegetative work
T5 lights best for seedlings
And yes he needs fertilizer but also needs trace elements and minerals.
