I'm starting to think feeding ducks is a lot like watering plants. You can water and it's good that you do but it has little effect compared to actual rain.
Similarly, we take great care to select really good quality food and feed dilligently, and then ducks forage 100% during a series of rainy days, don't even come looking for neither dry food nor grit, and we have glorious eggs.
The alien one above is probably waterlogged; it was found it a basin and you can see greenish algae on it. While we had basically 3 straight days of heavy rain and several new mini lakes on the property, I was not changing the water in most of the basins and this is the result.