It would be a good idea to filter out the developer to remove any large particles of amidol, which mostly have the effect of staining the back of the print.

The enlarger bulb might not be bright enough. Lots of people use 300-watt bulbs. I tried a number of light sources and settled on a cheap halogen desk lamp from Ikea with the UV filter removed, and my exposure times are usually 15-30 sec.