Camera meters are designed to average the light they see and make it a middle tonality. At night all that dark space make the meter to underexpose. We can correct that in camera or we can do it with editing software.
The majority of those beautiful shots are overexposed. The exposure meter simply did its job trying to average the exposure to a middle tonality resulting in overexposure.
With your kind permission I corrected one of the shots and I hope you can tell the difference compared to the original.
It is never my intention in this forum to critique unless the OP requests critique and when I do critique I am only doing it to the best of my knowledge to help. If you do not want critique or if you are satisfied with the quality of these photographs simple ignore me and I apologize.

We will be going on an Alaska cruise at the end of May. I was looking at the Tamron 16-300 as there is a rebate going on right now, until March 5. A local camera store showed me the Tamron 70-300 f4.0-5.6, saying that would be better lens. It is normally priced about $50 less than the Nikon 70-300, which is an f4.5-5.6. However, another local store is offering. $30 rebate on the Nikon, bringing the difference in price to only $20. For $20 (even at the regular pricing) my gut feeling is to go with the Nikon. Only other major difference is that the Tamron takes a 62mm filter while the Nikon takes a 67mm.

Sorry if I "hijacked" the original poster's question but your comment on the 70-300 got me going.