A couple of observations on your exposures. You didn't give the binning so I will assume 1x1. Most cameras are more sensitive to green so you may be able to cut back on green exposures. On my camera, I find that if I do green at 80% of the other colors, it is almost color balanced. Since filters reduce the amount of light, it is often desirable to have longer exposures for colors than for luminance. A rule of thumb is to have the color exposures twice the luminance. So depending on the camera saturation your exposures might look like this
L300; R600; G480; B600 or perhaps L150; R300; G240; B300
Lastly, consider using PixInsight for processing.