So sorry for your loss...I've never seen anything quite like it. In the future, if you're unable to get a bird packed up for necropsy on the same day it dies, you can double bag it in heavy duty freezer zip lock bags, refridgerate (don't freeze) the bird overnight and then ship in the morning...
The best results I've had with scaly leg mite is with Scarlet Oil...it's actually an equine product, in an dark blue aerosol can. Very easy to apply and if you're treating more than one bird, the fact that it's tinted pink helps keep track of who you've medicated and who still needs treatment...
Hi...can you tell me how much these birds have been handled? Are they resonably tame or are they flighty? I might be up in Sacramento on Friday or Saturday. These are bantams, right? What do you want for them?