Id throw out the 420nm and replace with a 460nm bulb so you get more PAR. PAR is much more important to consider than watts per gallon. Since you have a t5 HO
fixture, get two ATI bulbs and you should be able to have much more coral than your current setup can support. ATI makes a Blue Plus bulb that has an awful lot of PAR AND gives you the same effect that an actinic 420nm bulb has.
Id go for a 10,000k ATI and an ATI blue plus. Might as well get the max you can out of that fixture. Now, why are there 22in bulbs in a 30in fixture?