No ducks are going to do well with that many drakes around. It may work out right now, but when breeding season hits, those four drakes are going to all be after the same thing--and drakes are almost never kind maters. I'd get rid of three of them.
When they produce depends a lot on your location. They can start as early as seventeen weeks, but you have to have the right weather, and a good strain of ducks.
Ducks lay where they stand. Or sit. Or swim. Unlike chickens, they usually won't use nesting boxes, unless they're about to set and raise young. To combat egg loss, many people leave their ducks in the coop until nine in the morning (ducks lay early).
Duck eggs have a very thick bloom, and can take a bit more washing than a chicken egg can. If they're dirty, use hot water and store the eggs in the fridge. If they're clean, you can just leave them out on the counter (they dehydrate faster in the refrigerator.)
You don't need to candle unless you're hatching. You can use a light to look for imperfections in the eggs (sometimes, a clot of blood gets into the egg) but if you're not selling, why bother?
As for feed, you should compare your tags to this list at Metzer Farms and see if you can spot any deficiencies.
https://www.metzerfarms.com/NutritionalRequirements.cfm For start, you should knock your protein up to 18%. Any good allflock feed should work. Chicken grower is a thing I would skip.
