They look like aphids to me. I have them all over my peas. I sprayed them with insecticidal soap. Too soon to tell if it worked.

Thank you, I looked up aphids and they look exactly the same to me. I will spray them and see how that does. Hopefully they are the root cause of my leaf problem and my yellow plant problem.

Are the aphids causing the black lines and "scaling" on the stem or is that something else that I am causing?

Neither aphids nor spider mites can cause holes on your plants, their mouthparts are not capable. But yeah, those in the picture are aphids. Sider mites, btw, are so tiny you can barely see them with the naked eye.

The reason I originally thought spider mites is because I would see little red specks moving around on the underside of my leaves. Not a lot, just one at a time, but they would be on just about every plant. I was trying to take a pic of those when I found the aphids. I also have very little white bugs on the underside of my leaves too. But most of my plants have holes in the leaves. I have never seen caterpillars on any of my plants, and they are really thin, so I can't figure out what is causing it.

Aphids, and maybe something else. The simplest method of control of Aphids is a sharp stream of water to knock them off the plants, which can also help if you have Spider Mites and some other insect pests.
There are a number of insects, both pests and beneficials, that could be making holes in leaves that do not stick around. It could be slugs making those holes.

They look like aphids to me too. Blasting them with water only moves them around, and they'll surely crawl back up again, so that really accomplishes nothing.

How about squishing them in-place on the leaf, or putting them in a jar, then squishing all of them?

"Blasting them with water only moves them around, and they'll surely crawl back up again, so that really accomplishes nothing. "

Not true. Aphids are such soft bodied critters even a spray bottle will do some damage although a hose is more effective. From Colorado State University:

"On shrubs and garden plants, aphids can sometimes be managed by simply washing them off of plants with a forceful jet of water. Hosing plants can lethally injure aphids and very few surviving aphids that are knocked to the ground can successfully find their way back onto their host plant."

tj

Here is a link that might be useful: Whole article