Help me find out what's going on

[Fritz77]

Well, it looks like the tomato season is almost over for me. Over all I can say that my second season as a tomato grower has been better than the first one. For many reasons, I couldn’t take good care of my garden in the last month and the result was lots of weeds and a garden that looks kind of abandoned. All I did was picking some good tomatoes and watering those plants sometimes. So now I was basically expecting my plants to slowly die as they did last year. What I wasn’t expecting is this strange look that ¾ of my plants have. It looks like they’re dying from the top. The top leaves turn yellow and then fall down, while the stem tends to turn into an unhealthy brownish color. I first noticed this in a row of Red Brandywine (not true to type since PL) when the season was still in full swing (see first 2 pictures). Now it has spread to many other plants. The temperatures have been around 75° F during the day and have dropped to around 50° F at night. I would say typical weather for this time of the year.
Is this how it should be or is something affecting my babies? What would you do if you were me especially considering that this is where I will grow tomatoes again next year? Please excuse me also for the poor quality of the pictures.