I personally wouldn't touch Euk (Iams) as it's additives affect many dogs, mine included, and can make them hyper, making it an unsuitable food let alone the ethical issues. But if it suits your dog then that's fine.
She should be well off puppy food now anyway - about 9/10 months should be the time for adult food for a cocker.
Personally I think this move to produce breed specific foods, Iams are not the only one, is putting yet more pressure on owners for what they "must" feed their dogs when it's not necessary. Not all Cockers are prone to weight issues. My jasper is much thinner than Buddy and always has been/will be, it's his make up - so feeding this would see Jasper being even thinner while Buddy's weight would be under control. Mmmmm - it's under control now because I simply feed him less than Jasper - sorted. They are simply capitalising on another emotive subject where we will feel we are not doing the best for our dog if we don't feed this breed specific food because our breed needs such specific dietary requirements. News flash - they don't!