I'm in agreement with those that like the Phoenix. I'm getting good growth under mine. Of course it's a 250DE sitting over a 25g puddle, but the ONLY coral that was light-shocked when I first put it on there 2 months ago was a micromussa and an acan. Nearly killed the micromussa. Every acro and monti I had responded well. I was VERY careful to acclimate them to this light though. Started at 10" high and used a sheet of acrylic covered in notebook paper, filled with punch-holes, for a couple days. Every day I'd tear off a 3-4" section of the paper until nothing was left. Now I have the light lowered to around 7" from the water surface.
I upgraded from a cheezy Nova Extreme 4X24 T5
If I had to make a guess on why your corals are suffering, it's precisely what you said--- they slowed growth with the bulb change and alk spiked up. The alk spike is more likely what the issue continues to be, not the lights.
When you changed the lights, it may have shocked them (too much light, a new Phoenix is pretty powerful at PAR production) and also different spectrum--- the Phoenix is WAY bluer than a 10,000K. So, more PAR than the old bulbs, and much more blue.... sounds like light shock.
As for what to do, you can try putting your old bulbs back in and stabilize your alkalinity. Get things looking good again, and slowly swap the bulbs and put some screen/eggcrate over your tank to acclimate them slowly to the new Phoenix.