Feeding melons.

I'd have thought a general purpose fertiliser would be one that is more balanced in the proportion of elements (nitrogen N / phosphorus P / potash K). Tomorite will be high in potash, as it is intended to stimulate flowering (and thus fruiting / veggies).

That being said, I'd have thought that a high potash feed would be useful once you have flowers starting.

A general purpose feed is often something like standard seaweed feed, if going for the liquid version. If using a long-lasting soil-based fertiliser, you'd be looking at something like Growmore or Fish blood and bone.