the first sympton is, he has a wet vent area, not too bad but we can see it is wet. So I cut off all the green in his diet for 2 days, and the vent still wet.
Then, I noticed that he might lose his weight a bit, although he still eating well.
And finally, he's kind of puffy, but only in very early morning or late evening, he stops puffing up right after sunlight go into the cage..
I am confusing between bacterial infection and protozoa...whatever it is, I need to find a treatment right before it's too late when all the "basic sick finch look" appears.

*edited* I've just found that maybe he had canker, details here:
http://www.ladygouldianfinch.com/features_canker.mgi



So I will much appreciate if you guys help me.
thanks alot.
Hoang.