Quote Originally Posted by albada View Post
I'll guess that the by-products of the phenidone and AA accelerate development. I remember reading about this, but this is the first time I've seen it. I'll reduce development-time a little, unless somebody has a different idea...
Is there a chance that the oxidation products of Ascorbic Acid are not acidic and that the pH rises as more silver gets developed? This could at some point cause some AA to develop on its own, especially in the regions which have already seen some development (Silver == catalyst), and the curve would look like the one you got.

A pH measurement before and after development and comparing these for test clip and whole roll would likely shed some insight. You could also test if consecutive test clips souped with the same liquid show increasing contrast (and pH), so you wouldn't have to expend whole rolls on this.

If my suspicion proves correct, better buffering would help.