Never had a Kessil, but I would just in general be careful with how much light you put in the tank. A 21g is relatively small, and LEDs can be deceptively powerful, i.e. they look normal from the side but are actually putting out very high PAR underneath. Your model has a 40w max, which is a lot of LED light for a 20g tank. Also, from what I see none of your coral really needs high light. I would start with about 10hrs of blue and then turn up the whites/others for maybe 2hrs in the middle and see how the coral responds.