The spotting on the leaves is a fungus, probably alternaria. It could also be a bacterial infection (Xanthomonas) - this second link has some information on how to tell them apart. Because sites disappear or move, I'm going to quote the relevent information from the second link so that it stays with this question:
[Fungal] diseases can be introduced to a crop through contaminated seed and spread from plant to plant via splashing water. Infections usually begin on lower leaves and move upward in the plant canopy. High humidity, overhead irrigation and close plant spacing promote long leaf wetness periods which favor disease development. Cultural practices to help minimize both diseases are similar – rogue out symptomatic plants, promote good air circulation and alter irrigation practices to keep foliage as dry as possible.
I would add to this that you should remove all traces of the infected plants from your garden to prevent them from possibly infecting next year's plants, and I would also practice crop rotation over a three-year period, if space allows. Because the fungus is transmitted via splashing water, mulching your beds heavily is also a good idea, although I've had mixed luck with mulching and tomatoes (they still get infected, but just later in the season).
This site also has a little more information and specifically recommends crop rotation, garden cleanup and changing the timing of any irrigation - although of course you have no control over the weather in your area.
Your plants are extremely stressed right now, which leaves them open to even more pest and fungal problems. The tiny red ants (are you sure they're not spider mites?) are interesting and may be attracted to the buds by aphids; these could also be the black spots on the stems.