Amazing Difference

As a new grower and taking advise from someone who should have known and didn't, I blindly followed him down a road to ruin. Luckily, I do watch, observe and learn as I go and decided to follow my own path. Below are 2 pictures of my seedlings. One is a seedling I grew for a month in a cup of Pro-Mix under a T8 and only given water. The other is one that I had started 3 weeks ago in 70% compost/30% Pro-Mix and fed only water and under an HPS light for the last week. See any difference? The first one is the compost seedling.