Need Help With Problem Plants

I'm seeing some problems on some of my plants.  If anyone can help me identify the problem and what to do about it, I'd be very grateful.

First, there are brown spots on some of my tomato plant leaves.   Interestingly, even though I planted four different types of seeds, the brown spots only appear on the San Marzano plant leaves.  Here are shots of several different plants:

Second, I planted several carrot seeds outside over a month ago.  Only one has had any significant growth and it was looking pretty good until yesterday.  Now the leaves are all mottled, like this:

Finally, I bought some succulents at Home Depot, which I planted in a container.  One of them is starting to turn an yellowy orange.  The first photo below the top part of the plant, which looks pretty much as green as when I first bought it.  The second photo is of the ends of the plant, which are now turning yellow.

Any help would be appreciated!