Experts and BHG readers answer.
Quickly Fading Flowers
If the plants have been growing in the same area for some time, it may be time to divide them. When they get overcrowded, they act just as weeds in competing with one another for nutrients and moisture. Late summer or early fall is a good time to divide the perennials that you mention. While you're dividing and replanting them, it would help to work in some compost to build up the organic matter in the soil. The extras that you get from divisions can be used to expand your perennial flower bed or shared with friends.
None of the plants that you mention should regularly need staking if they have adequate sun and nutrients.