It's probably the psyllium. I think this for a couple of reasons, you didn't start to see them until you added psyllium to your diet. Also, from my understanding, psyllium turns into a yellowish adhesive-like consistency when it comes in contact with water. That may be what accounts for the lighter color, but there are alot of different factors that can change your stool color.
A good test for you to try - stop taking the psyllium for 3-5 days, and see what happens. See if it goes back to normal.
Obviously, you would need to upload pictures before anyone can be for sure, but from what you described, I think it's just the psyllium.