I'm confused...you said it ate...was this via force feeding or did it eat on its own?
Baby ball pythons should eat with gusto- those who don't, its generally due to how they are set up - not surprising either, given that you set the snake up in a 29g with a 100w bulb.
Baby balls need security first and foremost...proper temps come next. A 29 is far too tall and long for a baby to both feel secure and get the right temperatures. High wattage bulbs also deplete the humidity in the tank quickly which will also have ill effects on your snake in the long run.