Why are my Shasta daisy blooms's middle turning brown, and the blooms stay small - immature?
Certified GKH Gardening Expert
In many areas, it has been very hot and, while shastas are normally very drought tolerant, this browning could be caused by too little water to deal with the heat.
It may also be a fungus.
I would recommend watering them some and then treating them with a fungicide to be on the safe side.