Extract NDVI from Micasense RedEdge-M

Hello everyone,

I’m working with plant phenotyping. I have a MicaSense RedEdge-M attached to a Phantom-4 and want to extract NDVI values from it.
I have generated an orthomosaic with my images, but when I downloaded it to calculate NDVI values inside QGIS my GeoTIFF image only has 4 layers, instead of 5.
I want to know if there is anything different that I could do to get the NDVI values.
The best thing for me is to export an orthomosaic with only an NDVI layer.

Thank you guys for your attention,