Oh Critter, you font of wisdom: I am growing (for the first time) amaryllises that I over-summered. Should I be fertilizing them now, or should I wait until the blooms end and they are outdoors in the sun.
As soon as they have foliage, they'd probably appreciate fertilizer. There's no need to wait until they're outside for the summer. Fertilize them while you continue growing them inside; treat them like a houseplant. I add time-release fertilizer to my potting mix, and when I water sometimes I also add water-soluble fertilizer at about 1/4 strength.
I'm glad you're having fun with your amaryllis bulbs!
I'd wait until they're done flowering and have started putting up leaves. As I understand it, the flowers and the energy to put them up are already present in the bulb. I don't think it'll help to add fertilizer until leaves are present to make more food that can be stored in the bulb.