It looks like it could be the lens... but I would still try what Hugh suggested! Without any FILTERS! You said you shot with a polarizer, right? Unless you spent some cash on it.. that could be causing an issue. I am assuming you don't have a UV or anything else on the lens either, right? Also for testing.. either tripod it.. or get that shutter up higher!
No, no nd filters, and no uv. just the polorizer.
I am not negating your suggestions, but I have done soo many tests, with...without...etc. I just used this one I shot today as an example.
my next test I will go back to bare lens, on a tripod, using examples stated here and see what I get.