Hosta, most perennials, and particularly some of the herbs will not need much fertiliser. If they are doing fine with the fish emlusion then keep using it. Of course you might find they would do fine without it, depending on your potting soil.

Fertiliser requirements for your fruiting plants has been extensively studied, both the timing and the proportsions of the nutrients. Note the references to farmyard manure (FYM), there really is no substiute for the time-tested solutions :)

Here is a link that might be useful: Nutrient requirements for tomato, eggplant, and peppers