I have a mallard duckling that is 1 week old. It has been in the house all it's life because we want it to bond to humans. The nights have been in the upper 50's outside, but recently the temperatures drop to the lower 30's. The first couple days I had a 100 watt bulb on it. But that bulb blew and now it has a 65 watt bulb. This morning we found the duck sneezing and with heavy breathing and runny nose.
I really love this duck!
1. Is it the cold that's bothering the duck? Or something worse?
2. We have Sulfadimethoxine that we use for when our chickens get sneezy, it always works, and I was wondering. Can ducks have it? If so, what is the solution for ducks?
An expert answer, please!

1. Is it the cold that's bothering the duck? Or something worse?
2. We have Sulfadimethoxine that we use for when our chickens get sneezy, it always works, and I was wondering. Can ducks have it? If so, what is the solution for ducks?
An expert answer, please!