Ok, I found a fix for this. The stretch is adjusting the histograms for the RGB data, but it is relying on an incomplete data set compared to the composite image you made with the Landsat data. What you need to do in the symbology is make sure your RGB bands are correct for the Landsat source, then under the 'statistics' tab choose "custom" from the statistics drop down. Now you can enter the min and max for each channel, if you set these min and max values to match the unclipped composite image you made, the colorization should match. I had the same issue and this solved it.