Video quality issues while uploading on Facebook, whats app and instagram

I am using iphone 12 max pro.

I recently try to upload video on what’s app, Facebook and instagram but quality of video is showing very bad,dull, and dark compared to originally recorded video.

video looks good on phone but it turns to dull and dark while uploaded on what’s app, instagram and Facebook.

please advise or help to fix this issue otherwise there is no point of using iphone 12 pro max