IMHO, the most likely candidate is Septoria, given the heavy spotting on calyxes but none on fruit. Could also be bacterial speck, but that's less likely in hot, dry weather, or bacterial spot. Browning edges could be aggravated by overfertilization or hot weather.

There's a ton of information available on options for these diseases, depending on how organic you want to be. But most options available to home gardeners don't cure-- just prevent and delay. We're well into your season, so if you get on this now, you should still be able to bring in a decent harvest. Prune off affected foliage, and spray the entire plant (fruit, flowers, stems, both sides of leaves) regularly (weekly, making adjustments if there is rain to wash off the treatment). This should slow down the progression of the infection so that your plants have a good chance of surviving and producing until frost.

Also, liquid fertilizer washes out easily. Get a tomato appropriate fertilizer (not so high in N, higher in P and K) and keep fertilizing, just not as often as you were doing before.

That is great info, thanks Gorbelly! Somehow I had not come across Septoria in my research, but now that I'm looking it up it seems to fit very closely with my symptoms.

So far I have stayed 100% organic, and hope to keep it that way. I'm a little hesitant to use copper even though it is organic.

I have some cornell formula that I made to protect my young cucumbers from powdery mildew. It sounds like some people have had success with it slowing Septoria as well. I think I will try that and see if it slows the spread.

Its actually drizzling today for the first time in a while. Should I wait for the leaves to dry thoroughly before pruning off the badly affected foliage?

Thanks so much for your help.

When you prune isn't that crucial IMHO, but you do want to be able to spray right after you prune, so do it at a time when it's not currently raining.

I use Bonide organic copper and alternate with Serenade. I have no disease on my plants this year, but that could also be coincidental, as a lot of people report lesss disease pressure this year. From what I understand, there's quite a bit of misinformation out there about Cornell formula. For one, it's potassium bicarb, not sodium bicarb, that was found to be the more effective ingredient, and it requires a spreader-sticker to work properly. AFAIK, it's very effective against powdery mildew but there's much less agreement about whether or not it works on something like septoria.

OK, good to know. Thanks again for the great info.