Why is my ball python suddenly acting different?

My baby ball python was sick recently and I've gotten him to start eating again and he seemed to be doing better. I also had put some recommended medicine into his water dish which I'm sure helped him. The thing is last night when I reached in to grab him he seemed very frightened and when I was pulling him out of the tank he was very skiddish and tried to get away. I set him down and he seemed ok, but when I was putting him in the cage later he once again went crazy and was trying to get out. Usually he'll stay on my hand until it's down in the cage and slither off. I did notice the water looked a little yellow with some mold on the bottem (I know I know... I had forgotten about the medicine in it but I have since cleaned it). I know this is because of the medicine, but is the unclean water the reason Mowgli is acting strange?