Cooling + rainbow effect question

[SODA]

Hi, I almost built a projector.
I used benq 557 ver 2, lumenlab standard kit and bt28 metal halide bulb (400W).

I didn't finish the box, but I already tested it and I really liked the image. However I got a rainbow effect close to the center of the screen... When I moved rear fresnel I the rainbow would move to different places of the screen. My configuration is fresnel->lcd->fresnel.
How to fix it?

Another thing is my fan. It is very loud 110v 120mm fan. However it does the job.

I want to replace it with something quiet but powerfull at the same time. Do you have any tips on which fan and what CFM I should look for?
Or any ideas on configuration of cooling system...

Thanks a lot. The image looks very bright and sharp

- SODA