I know it seems like a good idea to feed them in hopes of getting them to look better, but you should always wait for your plants to acclimate and establish themselves before feeding them
In some cases, depending on the type of plant, feeding them when they're not properly acclimated can actually cause adverse affects!
For example, feeding a Sundew when it's not doing so well and not making dew could burn the leaf you're trying to feed.
Anyways, once your plants are ready, you could pick up some freeze dried blood worms (All natural, no added vitamins/minerals or whatever), soak them in some water till they're soft and give appropriate portions to your plants
(That's what I feed my plants anyways
I don't always drink.... But when I do... I drink Rainwater.... Stay thirsty my friends.