Ah, I just saw your photo of the lights and the setup - tough setup with the center brace. Not sure why I missed that before.
(BTW, my 50 breeder is old-school - braceless...weighs a ton though.)
So, again
if you plan to change the lights....
That brace is killing the effectiveness of your third light.
I think over time I'd...
...decommission the middle light a.s.a.p. - absolutely not worth the electricity and bulb replacements required...
...lower the remaining two to 6" off the water - or whatever the
minimum height is to still get complete coverage (no shadows)...
...and upgrade to Radium bulbs. Your ballasts (European) are perfect. With this you'll be at around 180 watts per bulb.
Use the lux meter to make sure you don't make any changes in the short term that are too big.
Use it to compare old and new bulbs when you switch them to see what differences there are.
Also use it to tweak your lights to try and get your surface lux peak up to 30,000 lux or even higher.
Again, again....this whole issue is very secondary to the flow issue in terms of importance to your corals.
-Matt