No, your flies aren't too big. I've had 12" char take 8" flies on numerous occasions.
That said if you want to fish for small fish, use stuff they are more likely to eat. I would try dry flies, ie;elk hair caddis in 8-14 and irrestibles in 12-16 and some nymph rigs ie; stones 2-8, hairs ear 8-14, prince nymps 8-14.
Mind you fishing the streamers will give you a better shot if you come into any big boys.
Perhaps the fish are too small