What is the problem with my bread?

While I cannot speak directly of your recipe, I can comment on what often happens in a situation like this.  That is, we simply get careless and without realizing it, make little changes that affect the final product.  I would go back and start at the beginning with your recipe and follow each and every step very carefully.  Should you find that you have not inadvertently made changes and that you are doing everything exactly the same way as before, I would then have to suspect the ingredients that you are using.  Something obviously changed or you would still be getting the same results that you got in the past.  Examine every little step very carefully and see if you can find that change.

Jeff

...bread hasn't been as good as they were before...

Seems to me like a fairly obvious case of something having changed. So the question becomes: what changed? (My guess is figuring out what changed will be a much much quicker route to a solution than looking at the loaves  ...especially as ways to make gluten-free bread vary all over the map, and only a few people have experience with your particular method.)

Some common possibilities for what changed are:

• as noted above: subtle shifts in your procedure
• the temperature in your kitchen or refrigerator (if you "retard")
• the flour or flour-like mix (different brand? different sack? different type?)
• the water (if you use tap water) - to pinpoint the problem, try buying a jug of spring water at your supermarket and using that for a few batches (although it looks exactly the same and you haven't heard anything and there was nothing in your newspaper, sometimes tap water is very very different than it was last month)

(Also, could you tell us your recipe in detail?)

It's difficult enough to consistently produce a perfect loaf of gluten based bread, the degree of difficulty of consistently producing the perfect loaf of gluten free bread is exponentially greater.

If you could post your complete formula and an outline of your process so we can take a look at what you're actually experiencing from start to finish and, perhaps, find something in the data that looks suspicious.

The amount of xanthan gum you use will be critical  -  to the extreme  -  and could very well be contributing the problem you describe.  It is also possible that you are over-proofing the dough.

I went back to this thread last year.  Funny, about the same time of year...  Which makes me wonder about temperature changes.

http://www.thefreshloaf.com/node/19693/i-have-made-200-bread-and-now-recipe-fails-help

I think you should keep track of air pressure, have you a barometer?  Also be careful about slamming doors, oven doors and room doors while the bread is rising and being baked.  Go back to your original recipe and check over last year's notes.   :)   

I've trying blowing up the pictures but I still can't get close enough.  Look closely at the crumb in the "failed" bread and in the successful loaves.  Don't look at the bubbles (yet) but in the spaces between the bubbles, the solid part of the bread.  What do you see?  What are the differences?  

Dumb question: are you measuring ingredients by weight (i.e. with a scale)? I ask because what's intended to be the same amount measuring by volume (those pesky "cups", etc.) often differs by several percent  ...enough to throw off your recipe. Sometimes it will work just right, and other times it will fail, and it won't be at all obvious what's the difference.  Volume measurement is especially a problem a) with fairly small batches and b) with gluten-free recipes.