That is leaf spot fungal disease. The disease lives in the soil so you will have a hard time getting rid of it. When you water don't wet the leaves because the water splashing from an infected leaf to an uninfected leaf or from the soil carries the fungal spores with it.

Pick up and dispose--in the garbage-- any leaves or debris that is infected next year. Picking off any infected leaves then will keep it under control. Mulch very well so the soil borne spores can't get to the leaves.

Spraying with a copper based fungicide will help.

For this year since you are so close to frost anyway, I'd cut them down and get rid of the tops--in the garbage--don't compost or you'll infect the compost.

Good luck

Septoria divaricata is the name of the fungus your plants have. It's not soil borne (as in coming FROM the soil), but the spores can be spread by wind, water, insects, and even birds. Good housekeeping will go a long way in helping control the problem next year, as oilpainter suggests. All of those spots are little disease inoculants, so you want to get rid of them.

The common fungicides on the market are likely to be labeled for the control of Septoria, just be sure to be a label reader. Next year, get it nipped in the bud before it gets to this stage.

Thank you both! Question: could this have come from the mulch that was applied this summer? Also, is the same thing affecting these plants (which are in a different bed):

While there are some that will disagree with this I would start, if I had your garden, with a good, reliable soil test to see what nutrients might be lacking in the soil that is allowing these problems to develop. More and more you will find good garden writers telling you that plants growing in a good, healthy soil will have fewer problems. Along with that soil test, your local office of your state universities Cooperative Extension Service can supply information about that, you can dig in with these simple soil tests,
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drainsâ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
which can help guide you in making a good, healthy soil that will grow strong and healthy plants.

Thanks for the advice, I will definitely look at the soil as well; however, there are some things I already know:

Structure - it's basically pottery clay mixed with rocks. When dry, shovels bounce off it like cement and I need to use a pick-axe to dig; when wet, it comes out of the ground as enormous clumps of clay about the size of my fist or bigger that are not easily separated and can be molded and shaped as a single wet mass.

Because of this, I have done massive soil removal everywhere that I have planted and have replaced the clay with a combination topsoil and compost. The kamlia plant in the photo above is in a planting hole about three feet wide and two feet deep with all the soil replaced.