More info would be a BIG help.
Just how recently did you set up the tank?
How deep is your 30g tank?
Were you using some other light before, or is this a new set up and a new light? If you had some other light, what was it (t5, MH and how strong)?
What power levels are you using now?
What corals do you have that seem unhappy?
OK, start with the power setting low, like 20% white and 40% blue, or anything close to that. Look at it this way, the starting point I suggested is 20% and 40%, add them together and you get 60. Any mix of blue and white that add up to something in the 50 to 75 range is OK. If your tank is 18" deep, be conservative and use the lower end of the range to start. Then slowly increase the power every week or two by about 10% to 15%. I've been using a T247 over my frag tank for 2 years now and I run 90 to 100% blue and 40 to 50% white. So I have 100% + 50% = 150.
Coral needs a good 6 to 8 hours of full light so the algae in the coral polyps (zooxanthellae) can do photosynthesis. More time than 8 hours probably doesn't help at all as the photosynthesis shuts down, but the extra time with bright light probably doesn't hurt either. On the other hand it's probably not wise to go over 12 hours.
