i dont thiink its a bug. at least im fairly positive its not. It appears to be a foliage disease.
I dont know this for a fact, but I too am having the same issue and came on here to investigate. I believe it is from the high humidity and high temperatures.
It almost looks to me like Grey leaf spot, or some other kind of similar fungus. ( i know thats more on turfgrass or corn...)
Take a close look at the crass, leaves on the trees, and bushes near your plants. are they also infected with the same disease? Because it was at my place. ruined the neighbors crop as well.
My plants do not have any deficiencies. so its due not lack of Potassium or manganese. and neither was the guys next door.
I hope there is someone on here with some solid leads on how to cure and prevent this fungus...
(sorry i couldnt be more helpful)
~G