You are comparing a 4 bulb unit to a 6 bulb unit(50% more par). Furthermore you are making a huge assumption that after a tank move, and an environment shift, that it was only the light that cuased your corals to get pale. Sorry but I disagree with that as a valid comparrison. All you have to do is take a par meter and you will see. Theres is no magic, its all in the numbers.
I am actually relaying my experience in switching from halide lighting to T5s that are brand new bulbs. I have taken frags out of the 300gal display from under 400W 14K Ushios ran on HQIs and placed them in a different aquarium (also 40 breeder) under a 250W 20K XM ran on HQIs and the corals kept their color. This tank has different water parameters than the display.
Whether it is the par or spectrum of the T5 bulbs, I don't know. All I know is the new T5 bulbs made my corals very pale (light) in color. After the bulbs break in for a few months it's not so bad. My corals will still change color under T5 lighting vs. Halides, but not go nearly as pale. The 40 breeder that the frags were switched to mentioned in my first post with pictures attached had the same water from the 300 gal display (no change in parameters). And we consistently swapped the water out to keep it that way. The temperatures were the same, but the flow was obviously different as well as the lighting.
The only comparison I made to the 4 bulb fixture, was to say that I wished I would've bought the 4 bulb fixture instead of 6 because 40 breeders are so shallow and in my opionion don't need much light and 6 bulbs is overkill. I also pointed out that four of our bulbs are the same bulbs being used by the poster. I have three different tanks all with different lighting that I have transferred my corals/frags to and I am 100% convinced the change in color is caused by the lighting for obvious reasons.
Par numbers are only going to tell so much about the lighting, but not how an individual coral is going to react to it. Look at my first pictures. I couldn't have been happier with how the birdsnests look. They were the only ones that approved in the change of lighting. The red cap next to them got very bright too, but then started losing flesh. As for me, I rely on experience.