Be VERY cautious and test with your filters - I used an ND .6 tiffen with my hvx and it turned green towels magenta and added a pink hue to white walls - strange thing was skin tone remained unchanged - very strange and I was able to recreate the issue.
you need to take the camera off auto white and sounds like when your on the long end of the lens your may not have enough light. using nd.6 your loosing 2 f/stops in just the glass then add the lens zoom factor.
I'm in the same boat. There are so many filters available and I am trying to figure out which 4x4 people just absolutely fall in love with. The filters you can't live without or you have no idea what you did before them. I'm shooting with the HVX and have my matte box and it's looking for some nice filters to be housed in it.
Any suggestions. There are plenty of brands as well. Some cheaper then others. Do you get what you pay for when it comes to filters or are lower priced filters just as good?
The staple 5 filters have been ND 3, 6, 9, Polarizer and an 85. With video an 85 is not very critical as you can white balance although I was reading about people leaving their camera in tungsten balance and shooting with an 85 outdoors to reduce noise.
Schneider brand filters are superior to Tiffen. They're classic softs and black frost filters are really nice. Get the basics first.