every night when I come home I put my 3 ducks in the tub to swim while I clean their cage. they are only about 4 weeks old but I always make sure it's warm water. when I came home last night the smallest one of the ducklings was just laying there. the symptoms remind me of a cold runny nose, sneezing, shivering and lethargic. I put him under a heat lamp and gave him baby vitamin drops. he seems to be a tiny bit better but what should I give him medicine wise?