It is my first time growing tomatoes.

I have a 2 1/2' by 1' rectangular container with a Big Boy tomato plant and a cherry tomato plant in it. The bottem has an area that water is stored so it will not dry out no matter the temp. I live in town but put it in an area that gets plenty of sun.

The cherry tomato plant is growing great and producing lots of fruit (less my squirrel problem) but my Big Boy plant is yellowing at the bottem. It has two tomatoes growing from the tallest branches. Should I let it keep growing upwards or start cutting the top off? It is getting quite tall and I am afraid it wont be able to hold such big tomatoes.

I am also wondering why it is yellow at the bottem and some leaves are wilted in the middle of the plant. The tomatoes growing on it look healthy and strong. If this is a disease, will it eventually effect my healthy cherry tomato plant?