I haven't played much with amidol. It is potent enough to be used in acidic solutions. You might or might not gain by adding TEA, but first I would start from nothing but some sulfite. I think the citric acid is mostly for preservation, but it naturally reduces pH somewhat. Rather than leave it in and add TEA or other alkali, I would go with the simplest solution for starters and see what has to be added to make it better. In philosophy there is the principle of Occam's (sp?) razor that says the simplest theory that works is the best. Shave it down and let it grow if necessary.