I'm far FAR from being an expert but I think your tomato plant looks pretty good. My tomatoes always have leaf spots and they tend to grow out of the problems as the weather warms.. Your watering and fertilizing sound fine. You could remove the affected leaves if there aren't too many and then watch and see if it show up on other leaves. Yes, I have heard it is a good idea to remove the bottom leaves if they are touching the ground as that is how a lot of diseases get on the plant. I do it and it seems like a good idea. I see you have some type of watering system, make sure water is not getting on the leaves.

I agree your plants look good. My only thought is that they might overwhelm those small cages if they get to any decent size.

I also say that I don't think your plants are diseased.
Those so-called "lesions" often are seen on older lower leaves..
I would just go ahead and remove them, as unhealthy plant parts attract diseases. JMO

Sey

Looks like mite damage to me when you enlarge the pic. Strip off the damaged leaves and dispose away from the garden. Check the undersides of new grow for any signs of tiny mites - might need a magnifying glass to see. If none discovered just monitor the plants for another week or so. If any signs spray with one of the several miticides available.

Dave

Thanks for the reassuring responses everyone. I'm relieved I don't have to go to drastic measures this early in the season. I'll check for the mites and keep an eye on it.

@edweather I got these cages for free, and as this was my first season gardening I already had plenty of expenses getting the beds up and running. First thing on the list for next season is a roll of wire to make some much larger cages. I'm hoping with some constant pruning of suckers going forward I can make these guys work.

Thanks again, and I'll update in a week with results.