I totally agree with what have been said about colour correction and microlensing.
Here is an example of a similar diffraction pattern caused by microlensing with the same sensor (from Jon Rista's website:
https://i.imgur.com/2ntiE8T.jpg
And my attempt at LRGB imaging with a 102mm ED doublet:
https://www.astrobin.com/full/105505/0/
Same target, same equipment, but narrowband:
https://www.astrobin.com/full/105131/C/
Also, 71mm aperture diffracts light more significantly than larger apertures and this will show as less-pinpointy (read: bloated) stars, unless larger pixels are utilised and we err on the side of under-sampling.
To sum up, IMHO, unless one does wide field under-sampled LRGB imaging, narrowband, from my experience, yields more pleasing results with a small ED refractor than RGB.