The term “bulb” has been used generically here. But clarification is required lest I lead the reader astray.
Strictly speaking, a crocus is not a bulb but a corm – a compressed stem. It’s similar to a bulb but has no scales. A nice visual can be seen at http://plantpropagation.com/corms.htm
However Galanthus is a true bulb or modified underground stem. A true bulb has scales attached at the basal plate.
Bulbs carry their own food within these underground stems and thus feeding them additional food is optional. Many give a sprinkling of bone meal or compost after the flowers have finished.
The true food they need is in the leaves that you must allow to die back naturally. Do not remove them until they have yellowed and will easily pull away when gently tugged. If flowering seems less than in previous years you probably need to lift and divide the bulbs or corms.
The word Crocus is the Greek name of saffron: Crocus sativus. Galanthus is from the Greek ‘gala’ for milk and ‘anth’ for flower referring to the white blooms.