Where can I find slow-release fertilizer pellets specifically for flowering
plants?

I have some pellets for acid-loving plants (which I use for my azaleas and
hydrangia), and some for roses, but I cannot find any for general flowing
plants.

I have begonias, petunias, hibiscus, lilies, sunflowers, butterfly bush, and
others.

What type of balance do hibiscus need? Do they like acid or basic soil?

- David