Just wanted to update everyone further on this.
Dr. Wyer called this morning. The preliminary results from the necropsy are showing that Dovey had a VERY severe inflammation of his esophagus. Dr. Wyer feels strongly that this could only have two real causes: giardiasis, or trichomoniasis (canker).
Cockatiels (as some of you know, I'm sure) can be "silent" carriers of giardia -- basically asymptomatic -- so there's a chance that CC had it and somehow it got transferred to Dovey. Usually it is passed via feces, however, especially in shared water dishes (which they never had). Still, it's possible, so I am hoping that's not what happened. Aside from that, Dovey notoriously pooped in his own water (No matter how much I changed it, he pooped in it) and he did get a weird "slime" in the dishes. I had mentioned this before, and to Dr. Wyer, so obviously again there is a chance that it came from that. CC's been given a water bottle (I'm working on teaching her to drink from it) but she's not using it yet. I've been making sure I change her water and ACV-and-boiling-water (and sometimes Dawn-soap, probably every three days) her dish. I'm going to be paranoid about that now.
On the other hand, birds with Giardiasis usually present with smelly poops, poor body condition, etc. Dovey, however, presented with great body condition, perfect poops, etc. If the Giardiasis was advanced enough that we lost him, it seems unlikely that he would have NO signs in his poop, etc. Also on the upside, it is frequently treated just as we were treating him -- with Flagyl.
The other possibility is that it was trichomoniasis, or "canker" -- it's common in pigeons and doves but is almost never seen in psittacines other than budgies. That would explain the swelling and saliva. Again, that's what we were treating him for....but maybe we were just too late. If that's the case, Dr. Wyer isn't worried about CC contracting it; it's very fragile in the environment, isn't passed by poop aerosolizing, etc. Pretty much, she said doves get it by sharing water, but MAINLY by feeding one another. It's usually passed by direct contact.
One way or another, if it's giardiasis and CC is a carrier (but shows no symptoms), or if it was canker, CC is safe and okay. Obviously we want complete results, but those should not be back for another few weeks. She said a "couple", and implied more like 2-3 instead of mid-July, which is good. We were just thinking about this....I'm glad she's kept me updated.
Right now I just am trying not to hate myself. I had this funny gut feeling when I first noticed his voice was scratchy, but no one else who heard him thought it was odd. And doves have vocal changes throughout their lives, so....I didn't trust my gut and I should have. We gave him the right meds, but in the end, it was just too late.
I should have noticed.
I should have tried harder, earlier, I shouldn't have waited to take him, I should have gone two months ago...
I'm sorry, Dovey....he was just so little....I promised him I would never let anything happen to him...
I was away for the week and only came back last night.. I am crying with you.. 
Fly free sweet little Dovey.. 
