You don’t mentioned what version of Media Composer you are using. But since v7.x, Avid introduced source side LUT control and I believe the default is to auto-apply a LUT on sources. Check your color transform settings.
In the meantime, when you AMA link to the files, go to source settings for one of your clips and check to see whether there was a LUT applied or not. If so, you can remove it, change it, etc.
Also in 8.4 you can change the target color spaces of the GUI monitors to be Rec 709, or take video ranges and scale it back to full range, etc.
In the end, you need to decide what luma range you want to be working in, and what you are delivering as a master – broadcast (16-235) or streaming (0-255) and color correct accordingly for your primary master.
Michael