The lighting schedule is what it is IMO. Coral needs 8-10 hours of daylight. Now adjusting your tank to a new intensity needs to be done "gently". some people use window screening to accomplish this, some change the amount of lighting the give to the tank. I don't think either way is wrong. You can do it by reducing the new lighting and slowly increasing over time, say going from 8 hours down to 5 and increasing and hour every 4 or so days. With the window screen place 3 or 4 layers of screen on the tank without decreasing you original schedule and every 3 or 4 days remove a layer of screen. I don't know what else you have in your tank as far as coral but if it is just the coralline you are seeing the problem with, it will come back with little intervention on your part.
for an example I have a 29 gallon BioCube. I took the stock top off that had 144 watts of PC lighting, and replace it with an open top and a 150 watt 14k HQI metal halide light. My coralline on the back wall was a beautiful purple color. It immediately bleached white. i did not change my light schedule or add the screen gig. the coralline over the course of a month started to turn a beautiful shade of green. Over the next few months it is turning light and dark shades of purple again.
Patience is the key in this hobby. Knee jerk reactions to get a quick result do not work.
I cannot impress upon you most that dosing is something that may need to be done but for the most part if you are not keeping a tank that is primarily SPS coral dosing will not for the most part be necessary. Regular water changes will replace most if not all chemical parameter to the needed levels to keep your tank at an optimum.
These are my opinions based on my reading and first hand experience, hopefully others will chime in with theirs and you will be able to devise a path that you can follow. Post some pics of your tank that always helps us to help you. If you are interested here is my tank thread.
http://www.reefbuilders.com/forums/n...beginning.html