Karen - if you have any varieties that are prone to drawstring effect, you might want to hold off on that fertilizer until AFTER your hostas are unfurled. Extra fertilizer and water tend to encourage the green centres of the leaves of such plants to grow faster than the margins can and the margins end up tight and tear.
I don't fertilize a lot. A handful of alfalfa in the hole when planting and maybe a bit of tomato fertilizer - weak solution of water soluble - to the new plants. A couple of times during the summer I might brew up some alfalfa tea. And occasionally I'll add Epsom salts to the water if they are looking yellowed with darker green veins.
