When having a problem with a large number of plants, you really have to look at such things as the soil, your watering practices, and other management techniques. Sometimes we have to go back to when they were planted to find out what we might have done wrong.

Rosemary, by the way, is a plant that does very well with infrequent watering.

"I water them daily" Overwatering produces exactly those symptoms.

Get a moisture meter and use it. Do not water the herbs until the top 3 inches of soil is reading "damp" or even "dry" on the meter. Then thoroughly soak them and leave them until they are dry again.

To give you an idea, I live in Phoenix, and my herbs are watered every other day, for 10 minutes from a drip line. And it's been well over 90 degrees.

thanks for your responses.Is it powdery mildew? Is there anything to treat the condition ? I have stopped over watering now.
The weather here is crazy too. It is cloudy, windy and drizzles on some days,otherwise it is sunny and warm.
My apple tree planted this season, too has powdery white stuff all over., the Indian Hawthorne leaves are falling and has spots on them, rannuculus plants have already disappeared, strawberry plants the leaves are turning brown,their blossoms are dying. To name a few issues.

Milk with water and a drop of dish soap helps with the powdery mildew.

Another recipe is 1 teaspoon baking soda to 1 quart of water and a drop or two of dish soap. Combine in a sprayer bottle and mist the plants. Repeat a few times at weekly intervals.

Another common contributing cause of powdery mildew is overcrowding, which inhibits good air flow. If your plants are jammed together, try separating them or removing some.

I have a rosemary plant problem, tho different than the poster's above.
Bought some last year, put it in a gallon pot. It seemed really puny and woody to me. No new growth.
In the late fall I brought it inside and put it in a sunny window. There was some small flowers, and then some growth on top- but it was curled and deformed looking. It's almost comical looking, wish I could post pic. Also noticed a lot of purplish leaves that died and fell off.
I'm thinking this wasn't a good plant to start with.
What do you think?

I am having similar problems with my Rosemary plants...in previous years they've done really well but for some reason are miserable this year...we did recently put in a new lawn and have been watering a lot to help it root; could that be why they are mad??
Thanks