You need to tell us a bit more Guest?

True! New plants or old? Watering? Weed killers used recently? Including weed and feed on the lawn? All sorts of potential causes, which we cannot see from here. Posting some pictures could help, as would an inventory of plants affected--as well as those NOT affected. Botanical names would help, also, to make sure that we are talking about the same plants.

Honey fungus, possibly, as well - are there any signs of that in the garden?