This is actually pretty reasonable.
Some points to look at here:
- refocus the telescope regularly. You are ever so slightly out of focus.
- Do ensure you are doing darks. Dark subtraction is critical for most sensors. It might have been the method you are using to subtract the darks that impacted your data.
- For colour try using median combine
- Use sum combine for your lum data.
Keep at it, you have started an interesting journey.