Sucks doesn't it? LOL
If they don't wanna swim your way they ain't coming no matter what you say or do. I would think that they saw something that they didn't like. Since they sat down relatively close I would guess it wasn't too big of a deal but something made them not want to sit with your ducks. May have been something was over there that they wanted, shelter from wind, food source, break in the current. Or it could have been something in your rig, lifeless decoys, movement in the blind, etc. In my experience, if they sit down across from you out of range they aren't gonna swim in to you. Now if they sit down just a bit wide they may swim in, but if the sit down really wide they've made up their minds. Sit back and hope somehting spooks em your way.