Generally, this year has been a bad year for tomatoes at least across the North. I suspect you had similar weather to me. Cool wet weather does not agree with tomatoes. I had my plants ripped out by Labor Day because of early blight. All the wet weather is likely to have splashed up soil on to your tomato plants which gave them a fungal disease (my guess.)

Rotten on the inside could be blossom end rot. This occurs when the plant can't absorb enough nutrients (particularly calcium.) This too can be attributed to all the wet weather.

I'm not beating myself up too much about the bad tomato season I had, but am looking forward to next year.

Here is a link that might be useful: Blossom End Rot

Certainly wasn't a good weather year to base one's experience with any variety and call it negative, much less blame it all on the heirlooms. ;)

As many of the posts here will show, hybrids has just as bad a year in many parts of the country as heirloom varieties. Molds, mildews, blossom end rot, bacterial and fungal problems run rampant in excessively wet and cool weather years. Some of it can be off-set by exceptional soil prep prior to planting and very careful feeding but you can't control the weather.

Your problems may be been compounded by getting a late start, by using poor quality transplants, and/or lack of time to properly prepare the soil or prevent disease problems but weather is at the root of most of your problems.

As to the mis-labeled yellow from Walmart - no way to know what it was as there are many possibilities.

I think, like you, many are looking forward to a better year for tomatoes next year. Good luck.

Dave