How have your temps been? Too high temps can cause blossoms to not set, and I have heard that Brandywine is very fickle in setting fruit. I have 4 brandywines myself, they were put out in April and set fruits when the temps were cooler(70-80s) here, even so, I had a lot of blossoms drop. I have maybe a dozen green fruits between all four plants, while most of my other plants are loaded with green fruit....just waiting on it to get ripe :-)

Our temps have been anywhere from high 90's about a month ago, to 50's a couple of weeks ago in the mornings, now they are normal, high 60's in the AM and low 90's in the PM.

Hopefully they will produce some more blossoms for you before it gets *too* hot. From what I have read and seen most tomatoes don't set much once the temps get above 90.
If they do put out blossoms again you can try to increase pollination my flicking or otherwise gently agitating the blossom.
When did you put the plants out? If you got them out a little late, maybe next year you can try get them planted out sooner so they would have more days that were conducive to fruit set.....we are getting into the 90s here, and nothing below it in the ten day forecast, so the bulk of my fruit set is probably done.....
You could always root some suckers from the plants and see if you can get a fall crop...Or just maintain those plants, and, from what I have read, the fruit set should begin again when the temps cool back down.

Here is a link that might be useful: FAQ: Blossom Drop

Thanks. I put them out the middle of March, but we have had terrible winds this spring, and then the temps have been all over the board. My plants are beautiful, just no blooms and not many tomatoes.

My Great Whites & Brandywines are doing this as well.

I was wondering if there is a chemical component to this? I've fed once with miracle grow last week after putting them down on May 8. I bought the expensive Scott's soil and have large pots on my deck with lots of drainage. We've had a lot of rain, almost every day in the Washington, DC area. Our temperatures have not broken above 90 for more than a day or 2, although that is about to change.

My plants on the deck get all day sun, somewhat intense in the afternoon, maybe I should bring them into the screened-in patio so it's indirect?

I am getting blossoms, but they seem to turn yellow & then break off just before the fruit starts to come in.

I have lots of leaves, big healthy plants, they just aren't going to fruit.

On the other hand, the good news is that my Marglobes, Black Krims, Patios, & Yellow Pears are all doing great ! Lots of fruit - 74 visible fruit on 7 plants as of last night (my 7-year old likes to assist the gardener :)

I was wondering if some chemical imbalance or any additive can help save my blossoms?

Thanks,
Mitch in Maryland