Do the plants have signs of disease?
Has the weather been cooler, warmer then normal?
Excess rainfall or drought conditions?
Are your bulbs in need of lifting and dividing?
A decline of flowers can indicate a need to do divisions on your plants.
Have you done a soil test? A soil test can tell you if the plants are in need of soil amendments or fertilizer.
Here are some links that will help you.
https://www.gardeningknowhow.com/ornamental/bulbs/gladiola/getting-gladiolus-to-bloom.htm
https://www.gardeningknowhow.com/ornamental/bulbs/lily/dividing-lily-plants.htm
https://www.gardeningknowhow.com/ornamental/bulbs/daylily/growing-daylilies.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm