tomato disease; what is this?

A disease showed up on one of my tomatoes today. Any ideas about that it it? I've sent pictures to the extension, but they take a long time nowadays. The leaves involved are on the upper part of the plant. The tomatoes are drip irrigated. I yanked the affected plant to prevent spread.

Looks like Septoria.

It does, but I thought Septoria started with the bottom leaves.  Spores or whatever bouncing up from the soil when it rains?

It hasn't rained significantly in a long time.

It does look rather like Septoria, but the spots are not as defined as I've seen in photos of Septoria online.

It's possible that it could be Late Blight.  Hard to get a positive ID without something sporulating, but the diseased portion looks right for that malady.....

It does not seem like Late blight: for one thing, it is not the right time of year, and for another, the weather has been consistently hot and dry. Two more plants have got it. The newest foliage is affected first. It starts with discrete small brown spots and then leads to a total collapse of affected leaves and stems.

Also, there are no concentric rings, as in Early Blight, and no yellow halo, as in Septoria leaf spot.

I'm still having trouble with this. I removed the first round of plants, and everything was OK until I found another plant with it today. The really odd thing is that the disease always hits the upper leaves first.