There are a number of fungal diseases that will leave spots on branches. If the leaves look OK, what is making you think that something is getting eaten? Need a better description of what you're seeing. Also where are you? As the weather turns cooler and wetter, tomatoes will decline.

The first picture would indicate hornworm as they can devastate a whole plant (as can deer). I would check carefully for hornworm frass. At this time of year they could have left the plant to go and pupate (the hornworms, not the deer) :).

The third picture almost looks like slug damage, but I would have thought that unusual. If there are no fruit on the plant, it might be time to pull them - depending on where you live.

looks as if it may be related to your watermelon issue. Don't think it's hornworms, if I recall they won't leave you any leaves, nor do they darken the vines. Would be helpful to know where you are growing.

Located in South Florida

the University of florida has useful information about growing vegetables, as well as many other plants. Vegetable gardening is challenging in Florida, especially down here in the southern part, but if you follow the guidelines from the IFAS website, it will be much easier. I have trouble posting links, but you can find the information by googling Florida Vegetable guide, or growing vegetables in Florida. You'd also be able to find the link, since it has been posted multiple times in this forum, of course, that's a lot of searching.

I pulled out last season's vegetable garden about 2 months ago (I still have sweet potato and just pulled the last of my sweet pepper plants last week. Very seldom do I have plants in the garden between May and October. I began then planting tomato and sweet pepper seeds in small pots. It's bean planting time and I've gotten leeks, short day onions, carrots, cabage, broccoli and heat tolerant lettuce (anuenue) to sprout. As it cools down(if it does), peas, potatoes and spinach can be planted

Much luck with your garden!

florida vegetable gardening guide

I think the problem is chili thrips..... they eat a lot of different plants ..... for a quick fix try spraying with spinosad..... but also check out how to control them biologically. We had a great speaker at our rose society meeting and the gentleman gave a GREAT presentation. He brought a special little pepper plant with cornmeal that attracts a benefial bug that supposed eats chili thrips.... his research is just beginning but looks promising....