Lots of bulbs: glads, daylilies, star lilies, did bad this year...most did not bloom.
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.