A few weeks ago, something got to my 4 ducks. Three are missing & I found one on the side of my house with no head. I was devastated. A couple weeks ago, I got 5 new babies. A cayuga, a mallard, a pekin, a welsh harlequin & a khaki campbell. We all know ducks grow very rapidly. However, my khaki hasn't grown at all! He runs around with the others, eats, drinks, everything! I thought maybe he could just be a runt. But over the last couple of days, I've noticed he has foamy, white, watery poop. Almost seems like nothing comes out but some foamy white stringy bubbles honestly. Is there something wrong with him? He doesn't seem sick but I put electrolytes & probiotics in the water just in case. I have attached a picture of the size difference for reference. Side note: I refer to all my babies except Harley as males until I know otherwise. My harlequin is a female.