Lost my sons favorite bird

[randymcone]

One of our Chinese owl YB's has died.
There was no sign of distress and at sometime since yesterday he ended up with green poo crusted on feathers around the vent.
We found him, wings spread, on the floor, eyes open.
I'm worried about the rest of my birds.
Is this cooci? Would Sulmet from the poultry feed store work?
Are there other brand names? Would Petsmart carry a med for this? I don't want to wait for a mail order treatment.
My 10 year old son is devastated and I'm really worried about our other birds.
Can someone please help?