Good Afternoon,
From the pictures it looks like your daisies have Septoria fungal infection.(Septoria leucanthemi) surfaces as round or irregular brown leaf spotting that may progress to yellowing and death. Rain or irrigation water splash spores onto the plants, where they need wet surfaces for germination. While the spots are unsightly, Septoria seldom causes serious damage. Frequently clearing debris from around the plants and watering them from beneath in early morning to keep the leaves as dry as possible are usually enough to manage the fungus.  I hope this information is helpful to you and thank you for using Ask an Expert.

Thanks Vicki!

You are welcome.  Good Luck!