When film gets old (as in >10 years past its due date), its contrast goes down, while fog density goes up. If you Superia X-tra is that old, then that's what you can expect from it. If that fog bothers you, add Potassium Bromide to the color developer (start with 1-2 g/l) to make it go away. Extend CD time to boost contrast while you are at it. Normallyboth measures would adversely affect color balance, but in your case proper color balance is likely lost already.