Mallard questions

Hi, it's my first time posting here and just wondered about the behaviour of some visiting mallards to my garden.

Over the last few weeks we have had a drake and hen visit our garden daily. The hen then began laying one egg in the middle of the lawn at dusk. They then would both fly off. This happened three times then we didn't see them for about a week.

Yesterday three flew into the garden. One drake and two hens?( I know it was the same pair as they had become quite comfortable around me ).I cannot find any answers on google as to why the male is with two females. The two females ate and drank then settled down with the male watching over both. This morning the second female arrived on her own? She ate and drank then laid down on the lawn.

I assumed the original hen would have nested by now and be looking after her ducklings and the male would have left her. His plumage has also changed and I have read that he will be molting now.

I am just quite confused and hoped someone on this forum could enlighten me.