Yep, seems like you're doing things right. KCs are very good layers and should start somewhere around 5-6 months old. At least mine have. If I had to guess I'd go with what others are saying here - they're laying but doing is somewhere you haven't found yet.
Alternately something might be...
Good general advice, but not an absolute. I've been keeping ducks and chickens together for about a year and my drake doesn't bother the hens. He also has two female ducks to keep him busy, however. If you keep an eye on your flock you may be able keep them all together.
When your ducks get...
I wouldn't recommend keeping them in with your plants. What they don't eat they may very well trample with their big duck feet.
Mine hid inside the tomato and potato plants which did a little damage and they sat on my carrots. Overall not too bad but I only let them in there for short periods...
Ducks grow MUCH faster than chicks. That can lead to problems like bullying/trampling.
I house my ducks and chickens together and I can tell you that they tolerate eachother but there is no love between species. As soon as the run door opens and they free range they're off to separate parts...
Lots to know since ducks are quite different than chickens.
I house ducks and chickens together but that poses challenges. Ducks are super messy and love to splash water everywhere. As a result I have a no-water inside the coop policy. For ducks that means no food in the coop, either, since...
You can go smaller on the duck house if they have access to the outdoors. My experience is that ducks do not want to be inside and will only go in there when they have to. I can walk outside at 2am and I'll see them out there in the run.
If you do go small, or even if you don't - I'd consider...
Since you're not getting them for egg production I have to assume it's to have as pets. For that purpose I'd avoid KCs. They're more nervous than other breeds.
Khakis will not fly away. And they're the best egg-laying breed out there.
They're not as pretty as some breeds and they're definitely more nervous around people but if you don't care about those things then they're a great workhorse breed.
I think that most ducks aren't going to be affectionate. You can get them to tolerate you but they're not snuggly.
Once they turn teenagers they'll bolt from you like you're king kong. Your best bet is lots of exposure. I pick mine up, even though they don't like it. But they do come running...
From my experience ducks are much less capable of escape from predators when compared to chickens. Keep that in mind when considering where they're kept at night.
If you want a no-fly breed consider khaki campbells. No wing clipping necessary. They're also great layers. A little shy, though. I...
I've been using generic layer pellets for years with no problem. There's no way I could keep chickens and ducks both and give them each their own feed...
Don't introduce the ducks to the chickens right away. Keep them separated by some chicken wire or similar. And don't do that until the ducks are a decent size. At least four weeks in my opinion.
Practically speaking there are alot of considerations.
Ducks are messy around water. Chickens...
As Amiga mentioned - you may want to get him a companion unless he can be around you all of the time. Ducks get lonely.
That's where things start to get complicated, though. If you have a boy then you'll probably want another boy. Unless you want three ducks, then you can have a boy and two...
As pets?
Ducks. They have more interesting personalities and are hilarious to watch. Such ridiculous creatures - waddling, shaking their butts, bobbing their heads, standing on one foot, and the quacking...
As livestock?
Chickens hands-down. Much easier to care for.
It seems unlikely that a duck would attack a chicken so violently that feathers ended up "everywhere".
They can and will bite off feathers but I've never seen a prolonged attack that would make such a big mess. Now if you saw primarily neck/head feathers missing then I'd say it was a drake...