I have 3 yellow Lab, and while 1 of them is the picture of health and eating well, the other 2 are skulking behind rocks and looking pretty thin.
One appears to come and look at food, but doesn't eat, the other one rarely shows it's face.
I did suspect that one might have been carrying (visible bump under mouth) but it has been over a week since I have seen either one feed.
Tank levels are great, and everything else is doing fine.