I've got about a dozen tomato plants of different varieties in containers on my northeast-facing deck (mid-Atlantic region of the US), which receives about 6 hours of direct sun exposure per day. Some of them have developed these black splotches on their leaves. Based on these articles on Southern Living and Old Farmer's Almanac, it looks like this might be a sign of Septoria leaf spot. Is that what this looks like to you all as well?
EDIT: Clarified orientation and daily sun exposure.
Yeah that's my guess as well. Doesn't look like sunburn.
Ideally you'd chop the plants or branches to prevent it spreading, but if you think the plants will fruit before it gets bad, you might just let it ride, then replace or sterilize all the soil before planting next year.