Koi can get startled very easy. Maybe, when the lights go on in the tank on something else is scaring them and they are banging around the tank. The koi going crazy might make scare the godfish which causes them to hit parts of the tank as well. They are new to the tank and probably are not used to your tank and all of the stimulation in the room yet. If this is the case, they will calm down in time. Just a thought.