We're seeing a lot of early blight on tomatoes & peas in our mesa neighborhood this spring. My neighbor two doors down and I both were fretting over these mysterious brown spots on the lower leaves of our veggie crops and couldn't positively identify it against pictures on the internet. She brought a handful of leaves from various plants to A&P on Baseline and they said people have been coming in droves with the same problem. They believe the hot-cold-hot and moisture trends made conditions perfect for it this spring. They said to use sanitized pruners and take off as much damaged material as possible, bleaching between cuts. Then, to spray what's left of the plant with a fungicide and they sold her something called Natural Guard - Copper Soap Liquid Fungicide.
Also, give the plants air circulation. Try to prune lower branches so leaves don't touch the ground.