You need to define what you mean by white and dark spots. Do you mean pure white and pure black. These will only be relevant if there were pure white and pure black areas in the scene which is unlikely

It is not how the neg looks that is important. It is how the print appears. Try a print at grade 2 or 2.5. If that looks to have full range of tones then the neg is right.

If the print looks muddy which is low contrast then you can adjust with variable contrast paper on this occasion and then consider longer development next time.

The only proper way to determine if your negs are correct for your camera's meter or handheld meter with this developer and your agitation routine is to conduct a proper film test but that's another subject.

Until you have seen most of your negs as prints I wouldn't make any assumptions about what to change You have used the development time given in The Massive Development Chart which is probably what Rodinal recommends anyway. Usually the maker's times for development are longer than most users who test their films actually use.

So I would avoid increasing development time until you are sure that the prints are low contrast at grade say grade 2.5- 3.