Old DD-X == fully developed, but very grainy negs

Last year I bought a bottle of Ilford DD-X at a local camera shop. I have a feeling it sat on the shelf for awhile.

I remember the results were pretty good when I first used it. But 9 months passed before I used it again in the past couple weeks. The bottle is about 2/3s full.

Both rolls of film I developed have the right contrast, but the grain is HUGE.

I also read a post on rec.photo.darkroom where somebody else also noticed that old DD-X results in big grain (but normal contrast).

Does this make any sense?

Possibilites:

1. Much of the sulfite is oxidized.

2. The pH of the developer is increased due to sulfonation of hydroquinone.

2 is easy to verify with a decent pH meter. 1 requires a bit of analytical lab work to determine how much of the sulfite is oxidized.