When blooming, daisies require lots of nutrients. Apply an all-purpose fertilizer every month during their growing/blooming season. If using a liquid plant food apply weekly. After blooms become withered, cut dead leaves and blossoms to stimulate growth and produce more flowers.
Like deadheading pruning and pinching allows plants to remain bushy and continually produce flower blooms and reduces plant over-crowding.
Removing overcrowding foliage and stems will allow plants to receive plenty of sunlight.