Without more information, it's difficult to say why your plants didn't flower well. Soil conditions, watering, the amount of sun/shade, the type of hellebores, how long they've been planted, etc., can all play a factor. You will get differing opinons on this, but I don't find hellebores require much in the way of fertilization. I plant in well-draining, fertile (organically rich) soil and mulch annually with whatever is on hand, generally compost.

Maturity of the plants and the amount of sun they receive will definitely have an impact on blooming - older plants and more sun than shade will increase bloom count :-))