Vertical cracking is caused by too much water either heavy rains or overwatering as the fruit is maturing. Some varieties are more prone than others.
Jim

Agree, and there also appears that something took a chomp out of the one on the right.

But I grew them in an Earthbox. How could they have been overwatered?

Earthboxes don't prevent overwatering, especially when exposed to rain. Best method to prevent overwatering is a fast draining soil less mix. If you use a peat based or soil based mix in your earthtainer, you can easily retain too much water from rain, or even wick up too much water.

The main function of an earthbox or earthtainer is to reduce the need to hand water. But a poorly built soil (including commercial peat mixes) do not prevent the soil from getting saturated.

I will consider carefully what has been said, but let me assure everyone, there has been NO danger of anything here getting too much rainwater for at least the last 4 months.

Good news ,slice that off and eat the rest yum yum

Capoman Earth boxes Do prevent overwatering as they have overflow holes in them.Also some incorporate a cover so the top does not get watered even in the rain.
I know of no mix that DOES NOT have peat in it.Even the 5-1-1 mix has peat in it.

I don't see anything wrong with those tomatoes. It is August or maybe the end of July when you took the picture. It is 105 or so here. Mine are sunburnt, shriveled, stinkbug scared and I would be happy with those tomatoes. Go to the store if you want perfect red plastic tomatoes. By the way an article in Science News said that green shoulder genes bred out of commercial tomatoes may be partly why they have no flavor. The green shoulders make sugar.

Here is a link that might be useful: green shoulders are good

dickiefickle, If you look around these forums you will see many people having issues with earthtainers with water retention symptoms. They may have holes to drain, but they also have a wicking system. If you have a soil that is too water retentive and wicks up too much water, you'll have problems. Using an earthtainer isn't foolproof and doesn't preclude you from building a well drained soil to go in it.

About peat, There is a difference between peat-based soils, and bark based soils with peat in them. Peat based soils mean the majority of the medium is peat. I have no problem with peat - as a small component of a mix, and in fact has a crucial function of water retention control in a bark based soil such as 5:1:1. But when the majority of the mix is peat, it holds to much water (or none at all - hydrophobic). That is why so many people have problems with peat dominant soils.