Right before the shoot i set the video settings to be 2.7k 30fps. Right after my flight i downloaded the original clips from my mavic thru the app. After the original downloaded to my iPhone and i hit the "i"  button on the app, and the quality states its 720p. Why did it downgrade? Does it downgrade if you download the original movie wirelessly? What am i doing wrong?

You probably need to have a read of the manual. You will only get the original 2.7k if you download to your PC from the SD card. You could get 1080p to your phone but you would have to change the settings to HD in the GO 4 app but then you cannot shoot in 2.7k.

As Jenee says when you film on 4k or 2.7k the only way to download that is to the computer. Phone will only download 1080 or 720 videos.

What the OP is talking about is using the Editor mode in Go 4 to download the original video file from the Mavic, not stream downlink video.

Perhaps when you download the original file it doesn't replace the downlink version -- did you look elsewhere in your album for the original video?

The particular iphone would need to support 4k and would need a lot of space as the videos could be several gigabytes.