One place I have found useful information on growing tomatoes and such is the grardening column written by Walter Reeves--you can find them on the Atlantic-Journal Constitution (Atlanta newspaper) website, home and garden section.

I think Mr Reeves wrote that the biggest mistake gardener's make with tomatoes is not mulching around the base of the plant with pine straw
or such. Its supposed to be important to keep the lower leaves from touching the soil and contacting fungus or other diseases from contact with the soil.
I mulch good and cutt off those very bottom leaves. The mulch also prevents soil from splashing on the leaves if you water with a hose (which you may not be doing) and you dont have to water as much when you mulch.
Eventually, later in the season the leaves start to get yellow and bad looking from the bottom up no matter what you do. I like planting more tomato plants than I could reasonably expect to use because a few just may up and die.

Thanks for the tip tedevore. I mulched em with some pine straw and cut the bottom leaves.

Squash are not normally an all season grower. They put on a lot of fruit and then die back. They are susceptible to a number of insect borne diseases and stem borers. The big picture of the squash plants looks like it is healthy. The one yellow leaf in that pic looks normal.

Tomatoes will begin to drop leaves from the bottom up. If your tomatoe leaves are yellowing at the bottom, that is probably NOT a sign of problems. Give them a shot of lime to see if that helps.

3 qts of water every day MAY be too much. Try 30 minutes of watering for week to see if it helps. BTW, you can start some squash seeds now and extend your squash harvest until frost. If you plan on preserving squash, here is a helpful hint. First plan on how often you will eat squash. If once a week, then you need 52 bags. If once a week and then one more time a week for veggie soup, then double that number. Don't save too many. They take up too much room in the freezer and you never use them all if you freeze all of the excess. Rather than heat a big pot of boiling water for blanching, which also heats up the kitchen and overworks the A/C, cut them in slices in a casserole dish, add some water and heat until hot through-and-through. Dip them out, put in plastic bags and let them completely cool before putting them in the freezer. It sure keeps you and the kitchen a lot cooler. You can do the same for okra, peas, beans and corn.

The white spots on your squash is powdery mildew, which they are very susceptible to. PM spores can be rinsed off with plain water before they infect the cells of the plant, or you can use Neem oil as a preventative/curative.

Thank you tsmith and rhizo. Awesome tips!!!!!!!