imagery - Increase contrast of merged Planet Labs scenes

I've download a few PlanetScope scenes from Celaya, MX.

Taken alone they have a good contrast.

Then I've merged them with gdalbuildvrt, which lowered the contrast: Link

I've thought, that I could revert this again by stretching the contrast after this guide. gdalinfo -mm test.vrt gave me:

Band 1 Block=128x128 Type=UInt16, ColorInterp=Red
Computed Min/Max=664.000,48804.000 
Band 2 Block=128x128 Type=UInt16, ColorInterp=Green
Computed Min/Max=3688.000,30697.000 
Band 3 Block=128x128 Type=UInt16, ColorInterp=Blue
Computed Min/Max=19.000,38786.000 
Band 4 Block=128x128 Type=UInt16, ColorInterp=Undefined

Computed Min/Max=2521.000,39791.000

So I've stretched the contrast with GDAL

gdal_translate test.vrt out.tif -scale 664 48804 0 65535 -exponent 0.5 -co COMPRESS=DEFLATE -co PHOTOMETRIC=RGB

but the result has even less contrast: Link (all export from QGIS).

What went wrong?