First thing know when dealing with lighting, just because a particular light seems brighter doesn't mean it is better or that it is producing the right color for the given job it's being used for. As I stated before our eyes are really poor at determining brightness in specific color ranges. The Galaxy light spectrum has a lot more reds and yellows in it than the MH does. The Phoenix lamp when new has a significantly higher output in the sub 400nm to 450nm ranges than the Galaxy, however as the bulb ages its lux output will drop and color will shift some bringing in more of the yellow and reds. Zooxanthellae with chlorophyll b (what's in most corals) respond the most positively to light in the 410/30nm to 453nm range. Zooxanthellae with chlorophyll a respond best to light in the 640-650nm range commonly found in most types of algae. The Phoenix 14K bulb like most high quality reef lighting is engineered to maximize color output for chlorophyll b. That is why atinic marine lighting is used, but we humans prefer much softer colors in the 4-7k or daylight range and that is where most of a light's perceived brightness comes from. Chlorophyll b will not make much use of the warmer colors, so light output in that range is more for our benefit than the corals. The Phoenix 14k lamp having most of its light output set in the 400-500nm range and a small spike in the 640nm range will not appear as bright to us especially when comparing it to the Galaxy due to it producing far more light int he lower range than the Phoenix, but that doesn't mean it's not producing a ton of PAR especially at shallow depths. The fact that your sps corals are bleaching at the tips is likely proof of that. The other cause for the bleaching could be just to the sudden change in the color spectrum that stressed the corals a little bit. If anything I would replace the bulb, only because you don't know the run-time hour count on it, and if possible raise it up another inch or two for a few weeks and then slowly lower it back down.
As for the buzzing and flicker, yes that's normal. MH lights make noise, especially in fixtures with older bulbs and ballasts. The buzzing sound when first powering on is typically the capacitors heating up and/or coil whine. The flicker is usually caused by the arc in the arc discharge tube swirling around as the quartz glass heats up. This can take up to 90 seconds or more depending on the ballast and bulb to reach full power and normal operating temp. If you have access to some welding goggles you can watch it swirl around the tube, it's kinda neat.
