Daisy Death

I've really enjoyed my Shasta daisies’ bloom. A fellow gardener gave me three plants this spring. I placed them by the front walk where I could view their cheerful blossoms. The plants have bloomed in succession, giving me a long flowering period. Unfortunately, the first two began to die soon after they reached their bloom peak.

When the first plant started browning, I thought I had under-watered it. When additional water didn’t help, I was afraid I had over-watered it. Later, I became convinced that the roots had been fatally disturbed by a mole. Now, the second daisy has begun to die and I've seen no evidence of mole activity. I'm at a loss. The plants seem perfectly happy until they begin to set seed. They exhibit no obvious symptoms, such as pustules, bug infestation, or mildew. They just look like they are drying up.

I my gardening frind and he says it may be a fungus. I’ll admit, I haven't carefully inspected the plants and could have missed a fungal inspection. He says that this summer has been particularly good for fungus (bad for plants).

My third plant is blooming now. I’m afraid that it will also wilt and die soon (like the plant in front of it). Perhaps this picture holds the clue. Has anyone else had a similar experience with Shasta daisies?