I would remove the leaves. Sounds like Early Blight to me.

Bugs may be aphids...spray 'em off.
Aphids suck the plant's juices...not a friend.

It's a bit of a reach to make a disease diagnosis without images.

Any chance of posting some?

It is difficult to make a disease diagnosis even with good pictures. Without pictures it will be just a guessing game.
JMO

If you do nothing else remove the damaged leaves. Nothing is gained by leaving them on the plant. Lots of pics of aphids on the web you can browse to see if that is the bug you see. Then act accordingly.

Dave

I will try to take a photo and post. I've been unable to take pictures the last couple of days because it's been raining. I'm confused by the bugs -- mostly I read to knock the aphids off with a blast from the hose -- this seems to make sense with normal aphids but does it work for flying ones? And also seems to conflict with advice not to wet the leaves in order to curb spread of fungal diseases. Any advice on this one?

Gardening is a balance. Nothing directly conflicts with anything else in reality. It is all in the timing and the context :).

Sure you don't want to wet leaves anymore than is necessary - so avoid doing the watering with an overhead sprinkler when possible. But the rain has already wet the leaves. So hitting some aphids with a water hose isn't going to make any difference, right? Had it not been raining then blasting the aphids with the hose early in the day when the leaves have plenty of time to dry out - no problem. Ok?

And yes it works on winged ones too as it destroys their wings.

Dave