How to improve the displaying of a multiband raster in QGIS?

Question

I have a multiband (WV3) satellite image that I'm displaying in false color (R=NIR, G=Red, B=Green) on QGIS 2.14. The quality of the results I'm getting via simply changing the band rendering in Layer-> Properties -> Style -> Band rendering --> Render Type: Multiband color are substantially different, and lower than using the SCP-plugin:

Regular rendering via layer properties:

Band rendering via SCP:

I need to do this programmatically via PyQGIS, so I can't use the plugin. I have also tried to play around with raster enhancement buttons but no success. Does anyone know how to improve the quality of band rendering?

UPDATE As pointed out by @user30184, the issue was the fact the max values were not updated in the band rendering (pressing the 'Load' button in the band rendering window). The problem remains - how to update the rendered min/max values via PyQGIS? My current code:

lyr = iface.activeLayer() #An multiband (8 band) raster 

lyr.renderer().setRedBand(7)
lyr.renderer().setGreenBand(5)
lyr.renderer().setBlueBand(3)

if hasattr(lyr, "setCacheImage"):
    lyr.setCacheImage(None)
lyr.triggerRepaint()

The 'Load' action that needs to be completed in PyQGIS:

Answer 1

Here's a solution to updating the min/max values after changing band order using PyQGIS:

#Change Bands rendering
#5-3-2 = true color /// 7-5-3 = false color vegetation
lyr = iface.activeLayer()

bands=[7,5,3]
lyr.renderer().setRedBand(bands[0])
lyr.renderer().setGreenBand(bands[1])
lyr.renderer().setBlueBand(bands[2])

if hasattr(lyr, "setCacheImage"):
    lyr.setCacheImage(None)
lyr.triggerRepaint()

contrast = QgsRaster.ContrastEnhancementStdDev #OR: QgsRaster.ContrastEnhancementCumulativeCut
lyr.setContrastEnhancement(QgsContrastEnhancement.StretchToMinimumMaximum, contrast, iface.mapCanvas().extent())