Beginner Gardening: Seedlings not growing, 2 by Mjh11

Mjh11 wrote:
So, I started these seedlings on 2/5. Out of about 250 flowers this is the only tray I am having issues with. All of the rest are in the jiffy pods and are doing well(some even about to flower). These, however, I started in regular sterile seed starting mix. Everything germinated nicely but got to the point in the pictures and just stopped. I figured since the seed starting mix is sterile and had no fertilizer they needed a boost. About a week and a half ago I hit them with 1/4 strength 5-1-1 fish fertilizer. I\'ve done that 3 times now and haven\'t noticed any change. Now I\'m thinking I need something a little stronger and was thinking about giving them and 1/2 strength dose of miracle gro or similar chemical fertilizer. recommendations would be greatly appreciated. Thanks in advance.

Ps the plants pictured are butterfly bush(the really small ones), new Guinnea impatien, and some echinacea. They get 16 hours of light a day and are kept between 70 and 75 degrees.