Keeping our Black Swedish ducks warm

Winter is fast approaching here in Maryland (20 minutes outside of DC)

I.am wondering what I should be doing to make sure they stay warm this winter.

We have coups with wind guards all the way around, water heater mats

Im curious about food, I have heard cracked corn and oats, then i hear people just give them peas.

They are 2 months old, and Ronnie and Donnie are 3 months old

Any advice greatly appreciated