Shrimp plants won't bloom

I planted shrimp plants 3 years ago in different gardens with light conditions ranging from light filtered shade to full sun. They bloomed throughout the first summer, but for the second consecutive year they won't bloom. Otherwise, they're healthy vigorous plants. Please advise.

After applying fertilizer with a high phosphorus content, I've finally gotten a few blooms on my shrimp plants. I would have more, but they were so tall and leggy, I had to cut them back. I'm rooting the cuttings, along with lots of lantana. So far, my african iris plants, though tall and robust, have produced no blooms.