that's odd....my parents had one to do the same exact thing, just die. I have one in an upside down container that is doing fine. My other plants which are not BB seem to be doing okay. I've got those 3 plants in buckets away from rabbits. :?
Sounds like tobacco mosaic virus. One day its pretty and got fruit on it, next day its a little wilty looking, next day its dead. If its this, you need to get it out of the pot and destroy it. Also expect more to die. Very contagious. Soil borne and mechanically spread.
Better Boys are good tasting tomatoes but they are not resistant to tomato blight, tobacco blight, veticulum wilt 2, fusarium wilt 2 & 3, or southern bacterial wilt. In my area, better boys are highly susceptible to wilt. If I grow this variety I have found it essential to raise the plants from seed since these diseases are easily brought to you from the nursery and improper handling of the plants. If, you see your other plants doing the same, don't plant any more non-resistant tomtatoes in the same soil since tobacco virus can persist for 100 years. Its a nasty bugger. But the problem could be any of the pathogens I listed and many I did not.
I just planted Roma tomatoes this year after I read that they were better in our climate. I can't get good 'maters anyway, until the fall. It gets too hot here in summer. We'll see how the Romas do. I hope to make up in quantity what I lack in size.
That'll do it every time. In my area the tobacco virus is really bad. When we first experienced it I saw several hundred acres of tomatoes destroyed because of it. It put one farmer out of business. Unless I take the trouble to grow the plants from seed I don't even try to grow any of the named varieties that aren't resistant. Now I mainly grow plants that have funky numbers instead of names. I guess since they don't have a name I get to name them.
Here is a list of tomatoes and their disease resistance that you may find helpful.