How familiar are you with using a CPL filter (circular polarization)? I couldn’t tell that you were using one, which makes me suspect that you are not terribly familiar with their use, so here are some tips on using it effectively. My apologies if you already know this and I’m being redundant.
It is not uncommon for the packaging not to explain how they work, so I run into a lot of photographers who don’t know. Remember that there are two layers in a CPL, the first is a linear polarizer, this is the workhorse, it limits the angle that light can enter the lens, reducing reflection primarily. The second layer is the circular polarization layer that circularizes the polarized light so that it will be readable by the camera’s sensors and electronics (like the metering). The linear layer rotates freely to allow you to fine tune that angle. Any time you rotate the camera, change the angle, sneeze, whatever, you have to adjust that ring to get the perfect polarization. At the wrong angle, it can actually increase the reflection and detract from the image.
ND filters are neutral density filters. All they do is reduce the light entering the lens without changing its properties at any part of the visible spectrum. The practical upshot is that you can use lower-light settings on daylight scenes. If you get them you’ll want a 1, 2, and 4 stop filter (these can be purchased as a set). Maybe an 8 later if you need one.