I would still have to say that something else is wrong if the trout never did feed very good even in the beginning. A healthy trout 12-14 inches could easily escape CC predation in 60 degree water. 3 acres is not necessarily a fairly limited space, and 100+ large CC is not overly stocked for that amount of space.

I am still thinking something else is going on/went on/early on. Or there could be many reasons why they havent taken to the feed, like the feed could be bad/old or it is too low of protein for the trout to eat, or the trout have taken to an alternative food source. Even if the CC have just gone crazy eating them, the survivors should still be feeding on 40% fish food fairly aggressively.