Earlier in the summer, they were being eaten by something leaving little black spots all over the leaves. I read that it was probably bud worms, but I never saw a single one, looking closely and patiently at all different times of day.

Now the black spots aren't as numerous, but the leaves and blooms are still being chowed down on. In the morning there will be a nice healthy bud, then it will bloom by the late afternoon, then at some point, some phantom creature will start gnawing on it, and the next day the poor plant starts the whole thing over again.

This is only happening in one spot. I have the same flower planted in hanging baskets, pots, and in the ground and they are all healthy and happy with lots of blooms. This planter is next to the house, built into the deck, and about four feet off the ground.

The snapdragons planted with the vinca are untouched. The wax begonias are mostly fine. Some leaves near the bottom aren't great.

There are a few tiny spiders that make webs between the plants. I've seen them hiding on the bottom of the vinca leaves. They are dark and they move with very quick little jumps. I started to think maybe they're the culprit, so I started getting rid of any webs I could see, and when I water, I make sure to hose down the whole plant, the planter and the siding where it meets the house. No luck.

How can I get rid of these little mogrels? I don't want to buy anything fancy, but I will if I have too. The plants look fine and otherwise healthy, but I want to see that color pop!
This picture was taken early this morning, when the pests haven't gotten to many of the blooms. I expect they'll be eaten to the nub by dusk.