How would I enrich soil in a small area where several plants are ?

What type of soil do you have? Rocky? Clay? You can amend most soil by adding composted manure and perlite to the soil.

Soil can be enriched at any time by adding compost. We also add manure and pine needles in the fall and let them compost over the winter and then till it in the spring before planting.

Add new soil, perlite for better drainage, good fertilizer, and compost.

try buying a beta fish, it requires really pellets once a week, i use the "dirty" fish water to water my plants. If I clone plants I use it pure otherwise I dilute it 50/50. Keeps cost down. You may consider depending on space, adding a second planter. If you can't go outwards you can always have a vertical garden. Happy planting.

Grind eggshells, mix with potato, carrot and chayote (the very best of them) on a blender and put under the soil as a compost. They will explode in happiness.

Roses love bananas. Cut up the peels and put under mulch . Scatter coffee grounds and crushed egg shells around plants. Wood chip and leaf mulch. Compost made from vegetable scraps.