Ok first tip. Get lower. Don't stand above your subjects and look down on them. It doesn't work for snooty kings, it doesn't work for photographers
The composition is a bit off on the little ducks. The brown one is a bit too close to the frame, as is the reflection of one of the ducks at the bottom of the frame. Overcast days don't really create the nicest water to look at either.
The swans. The detail is lost on the rear swan. You can't really make out its feathers. The composition is better on this one. However. The out of focus reeds don't seem to enhance the shot and the closer swan is too close to the frame. Swans are elegant creatures. Your photo should reflect that in some way. Whether its gracefully gliding across a lake, or in the worst place in the world standing out as a symbol of perfection.
Hope that helps