pics would help

If the tomatoes weren't turning color, they're not going to if the plant is dead. The ones that are turning color will ripen after being picked. Overwatering with poor drainage can lead to root rot. Once that happens, it isn't going to be OK, even after drying out.

Did you feed it before it rained? Eggshells are worthless as plant nutrient, Even by the dozen, except in the very long term. Fertilizing with magnesium is just shooting in the dark. Healthy plants don't die because of magnesium deficiency. Was the container properly sized? Could have just run out of room. I'm suspecting that the rain didn't have anything to do with it.

What makes you think the rain didn't have anything to do with it? All the research I've done suggests that it received too much water. I was told that it was a calcium deficiency from overwatering since it got so much rain. The pot is HUGE! About 26 inches across & 30 inches deep. It has very good drainage. I've been feeding it Bonnie organic herb & veggie food once a week since I saw the first tomatoes about 2 months ago. I know the eggshells don't work right away but I figured it was worth a try since I couldn't find any calcium in the garden centers I went to. Also, a couple of the tomatoes are starting to change color now and they are all still on the plant. I mostly just want to know if the tomatoes are safe to eat with the leaves being so bad off? The stalk still looks fine & healthy.

One day of heavy rain is not going to kill a tomato plant unless it was sitting in standing flood waters. Unlikely in a container that you report is well-draining. It's not even going to severely stress a tomato plant overnight. Chances are whatever the problem was was already happening before the rain, and the timing is coincidental.

Now, plants can start looking a little pale after a period of heavy rains because they need some nitrogen. They perk up well after being fed with a quickly available source of N. But, in my experience, they won't be turning totally yellow just from one 12-hour period of rain.

Your tomatoes will not be harmful to eat. If the fruit is blemished with pest damage or mold of any kind, though, don't use it for canning, as it may have affected the pH.

I'm puzzled about your assumption that overwatering produces a calcium deficiency. Calcium is pretty rich in most soils as calcium carbonate, and unless the medium is highly acidic, that stuff isn't very soluble. Not sure who told you that rain washes calcium out of soil, but that's largely incorrect. But maybe you're in a locale where there is acid rain? Even in such regions, acid rain removes calcium on a time scale of many years.

Some kind of blight is probably the answer. Was the original soil mix a container mix (presumably sterile) or did it include native soil?