Yes

thats really odd

Yes, it certainly is...

So let me get this straight. No matter what you do, you get that yellow light on the right hand side of the tank?

Simon

Exactly...

Ugh, using a lens of any sort between the bulbs and the tank that could be filtering out different wavelengths?

Any protective film left on the reflector?

Ron, no to both of those.....

Um ... Ok, so you've swapped the bulbs left to right. So we know it's not the bulbs. You said you're certain it is not the ballasts, or the timers, or any contact points. So what's left? Hmmmm, either it is the wiring itself, the sockets, or the reflectors (or did you already say it was not the reflectors? I can't remember). Or .... perhaps there is some feature to the tank itself that leads us to see more yellow on the right hand side.

Just a really wild, unpractical idea, but it's something I might try if I was in your position: Can you temporarily put your canopy on backwards? If the yellow side becomes the left hand side, then we know it's electrical hardware (wiring, ballasts, bulb, socket, etc.) If the yellow side remains on the right, then you've exonerated your lighting and the problem is elsewhere (impurities in the glass, algae, water currents somehow creating some kind of weird refraction, I dunno ....)

Tony, I did replace wiring and the socket. I dug up a picture from Nov 2 that has both sides being the same, so I know I'm not imagining this!! (thought I might be going nuts!)
My lights are on a suspended rack, so I think I can take the entire assembly out and turn it around. I hope the green follows, because if it isn't the lights, I have no idea what it could be. I made sure all the glass is clean, reflector is clean, and any other obviuos thing I could think of. I'll switch the rack around tonight and see what happens!

One last longshot that I can think of: have the ballasts always been in the same location? Magnetic field problem?