sick plants?

I don't know what to think of my Rhubarb. You can see they still have some lower leaves yellowing and withering. And they're still full of holes, though I can't figure out what's eating them! All I find on the plants are fireflies (but I read adult fireflies don't eat, or nobody is sure what they eat- is that true?) and ants.

But a good sign is that at the base of each plants, new leaves are growing. So they can't be that unhealthy.

Today I dug up all the leftover Pea plants; they were so dry and powdery looking I was afraid they had mildew, and trashed them instead of composting. I've put a few young Green Bean plants in their place,

 but the leaves already have a pale mottled look which I'm afraid is also powdery mildew.

 I'm not sure if this is my fault for planting in a spot already infected with mildew? or if the seed I saved harbored some disease...