Sick male duck

[Avachapman]

I have 4 ducks 12 weeks old all doing great until we had a heat wave. We have a wild creek that they swim in. Male just seem to be quite and stop following the others. He lays on the grass and watches and sometimes calls for the others very two hours he gets into the water and swims and drinks but not for long then he goes back. I know he is sick because he is letting me pick him up and exam him with out a fight I have not raised them picking them up. I have seen some green diarrhea I am guessing it is his. I have checked his crop nothing stuck in it but it is puffy. I just started electrolytes in water today this is 3rd day. any one got any suggestions?
I have 20 chickens they interact great no chickens and other ducks act sick just him. I am new with ducks Thanks

 

[Amiga]

Heat waves often precipitate botulism poisoning. Have you seen this?

https://www.backyardchickens.com/t/700526/flushes-for-aiding-in-toxin-removal#post_9508213