If you are dosing RS Colors C you are adding plenty of iron already, so the iron deficiency is not your problem for the moment. Your tank and corals are quite young from what I see, they need time and strong light as Randy mentioned. Once they grow bigger then you can start experimenting with micro-elements dosage. I would say from my experience with Acropora corals that there is noticeable connection between iron dosing and green coral color. But IMO the color iron influencing most is green, not yellow. If I want more pastel yellowish color of my green Acros I'm cutting iron dosage and in a week or two they loosing their deep green color and turn to yellowish-green color Zeo freaks liked very much. But not all of the green Acros could be influenced by iron from my experience. (IMO the iron has nothing to do with coral pigments, but rather accelerating growth of zooxantellae and their color in conjunction with yellow coral pigments give that deep metallic green appearance of some Acros.