Cats won't eat fancy dried food

Two cats, almost two years old (brother and sister). They eat Purina One or Pro Plan chicken flavor. I've tried several more expensive and supposedly better dried foods (Hills, Iams, Blue Buffalo, Orijen...) and they turn up their noses at all of them. Literally, seems the smell puts them off. They've lost a little weight and worry they need more calories.

Any suggestions for dry foods cats love? I do give them Pate now and then, they don't like the wet food with chunks, they lick around the chunks. I think they do get bored of the same food all the time, but when I try a different one they reject it.