One of my boys has what looks like a white booger/slime from the corner of his eye. I tried gently tugging on it because I thought it was a feather stuck in his eye. But it seems to be attached to the inside of his eye. I change my ducks’ water in their bowl 2 times a day and they get a kiddle pool full of fresh water every day. They can definitely wash out their eyes well every day. He seems to be closing this eye a lot. I dunked his head in a bucket of water 3 times just now but it’s still there. What might it be and what would you recommend? Thanks in advance for all replies!