Confused about your location, you've said you planted out in April (in the main forum), but you have zone entered as 5?? It really is helpful if location (state) information is included. This can be changed on your member page.

From your pics, I see early blight (fungal), as well as some mite damage. Maybe even some alternaria canker (also fungal) in the 5th picture -- but I'm undecided about that as mite damaged leaves will eventually crisp up and turn brown in spots.

The 6th pic, the one with the white spotting or 'sugaring' looks like mite damage.

Fruiting bodies for fungal spores/early blight (the bullseye-like spots) seen in several of the pictures.

The best treatment for fungal diseases is prevention, i.e. to spray when plants go out -- many, myself included, use Daconil. To treat now, remove affected foliage best you can, and use a fungicide per instructions (Daconil, for example).

Numerous posts/threads on mites, some recent -- with several ideas for treatment.

Here is a link that might be useful: problem solver thread

"I had been watering for 20 minutes every day. I've since cut that back to 30 minutes every two days."

Through a 5/8" hose? Since I don't know how many plants you have, I am not sure, but that seems really excessive. I rarely, if ever, water my tomato plants. I use deep planting, but, still, even with shallow planting, 30 minutes every two days ... Wow, what a water bill! Do I see no mulch? Splashing the bottom leaves with wet dirt every two days can't be good.

By any chance, have you been watering near sunset? That is a big no, no. The best time to water is just before sunlight hits plants. That is when plants need the most water and wet foliage will dry quickly thereby helping to avoid disease.

Thanks for the replies.

I'm in Denver, Colorado. I planted in mid April as my yard is a patio yard protected between two houses and often escapes the late freezes we have.

The plants get water from the lawn sprinkler system. I had been watering every day as we've had temps in the mid 90's with very low humidity.

I've been trying to add mulch in the form of grass clippings.

I'm off to find some Daconil.

Thanks again!

Note that hte "Ready to use" Daconil/Ortho Garden Disease Control in spray bottles has a nasty gloppy texture. Instead, buy the concentrate (which is 1/40th the price) and mix it yourself. 1 tbsp (3 tsp) per 1 gallon of water for tomatoes as directed.