This happened to my pekin duck and i was told by a local farmer to add a spoon full of honey to a 16oz cup of water mixed with niacin. By the next day my pekin was fine.
It's easier to find out on YouTube but i wouldn't try it because it could hurt them. Just by looking at them based on my experience with my ducklings i would say the one on the left is a male and the one on the right is a female. I've always found females to have a mean/tough look like the one...
They look like Pekins (pure white ducks), you can vent sex them or wait a couple of weeks until they get their voice: female ducks quack and male ducks have a raspy quack. Also the male pekin will grow bigger than the female and will have two curly tail feathers.