Rotten on the bottom is blossom end rot. It is caused by a calcium deficiency usually due to too much / too little watering. Have you been watering too much? If so ease up and the problem should correct itself.

As for the size of the toms, I can't say.

Well... I guess I can be watering them too much.. but here in NC last week, as most of the east coast, it was 100° and the leaves were wilted... so I watered them twice a day.. the temp. has come down a bit and it's not as hot... so I'm back to once a day.

Suspect your 50 in 50 (never heard of them) are cherry tomatoes. A lot of early tomatoes are very small.
Blossom end rot generally affects only the first to ripen. problem may well straigten out. But be sure to keep soil moist though not wet.

If you're not into totally organic, go back to Lowe's and get the spray that helps stop "blossom end rot". It's about $5.00. If you will list the varieties you bought, it would be easier to determine the size prolem. Also, when watering, go to the side of the container (away from the root stem, and poke your finger into the soil to test moisture below the surface. I use Jungle Growth and MiracleGro Moisture Control in my large containers with a small dose of North Georgia Red Clay that seems to sweeten the fruit.

You may want to check out the FAQ here as well as the many discussions about "BER" as they will explain that research over the past 20 years or so has shown that it is not due to a lack of calcium in the soil and that blossom set sprays will only work when the drop is due to cold temps - not hot.

Indeed lab analysis shows ample Ca in the fruit. As has been discussed here many times by Carolyn and others:

Inconsistent moisture is one inducer of BER and mulching can help, too much fertilizer is another one b'c it causes stress to the plant, and high winds can also induce it as a stress, but lack of calcium is no longer felt to be an inducer for the majority of folks unless their soil has no Ca++ or their soil is acdic, which binds up Ca++ in the soil and that situation can be fixed by raising the pH.

In the last 20 years or so there's been lots of new data to show that Ca++ is not the major problem. And it's the impact to commercial veggie and fruit growing that has led so many Universities, etc., to do that research b/c of the monetary impact on the industry.

Stop Rot has not been founbd to be useful. Directions say to spray it on the fruits, but the tomato epidermis does not allow any molecules to enter. If it did the mature fruits would blow up after every significant rain.Spraying it on the foliage is also highly controversial as many University studies have shown. Thanks Carolyn.

Bottom line - you haven't done anything wrong. ;) Avoid excess N fertilizers and try to stabilize the moisture levels in the soil as much as you can and then wait. It will go away all on it's own once the weather settles.

Meanwhile, the fruit with BER on the bottom, while not appealing in appearance, is safe to eat if you wish. Just cut off the bad spot.

Dave

Here is a link that might be useful: BER FAQ's

I suspect part of the problem is watering every day. In moderate summer weather (80-90 degrees) I water once a week. When it gets hot (95+) I'll go with every 5 days. If I water more frequently I tend to get mushy black bottoms on the toms.

These plants are in containers, mattml, not in the ground. ;) Container plants require much more frequent watering than those in the ground.

Dave

Did you use potting mix to plant them in?
If not your soil my be to heavy for the pots.... ie compacting
the roots. Roots need air as well. If this is the case, the
plants could well be water logged towards the bottom of the
container. This could lead to the BER and smaller fruit (although I suspect the 50-50 is a cherry tomato....)

Also, what color are your pots? I'm using brown, green, and black and have figured that those are all bad! White or light
colored are ideal to reflect heat and keep the roots from
roasting during the day here in NC.....

Lee