I like themed names, too. I name my ducks after local plants. Clover, Pigweed, Thimbleberry, Plantain, and Nettle (but not the stinging kindalways go with themes, for some reason. My cats are artists. My dogs are literary characters. My chickens are all flowers. My goats will be verbs. I'm adopting adult llamas who already have names.
The duckies? I'm thinking either fruit or colors. Weird, I know. Fruit: Persimmon, Clementine, Fig, Mango, and Apricot are all possibilities. Colors: Scarlet, Sepia, Olive, Cyan, Sienna are all possibilities.
And there are always gem stones: Ruby, Opal, Pearl, Peridot...

Clover was a cayuga, black with a green sheen, and I used to tease her when she ate clover plants.

I have also found my pekin to have a lot of health issues. Though my other ducks have also had many problems, it is my pekin who our lives revolve around keeping alive. She's also got a great personality and is always the first one to forgive me for giving medication. The theory is that because pekins were bred as food animals no consideration was put into their health past the processing date. This can be really hard for those of us who consider them to be adored pets.