My little female Welsh harlequin duck has just suddenly fell ill, I'm not sure what's wrong with her... The other day i noticed she was looking a bit slow and not like herself... so i picked her up to take a look at her, and she was sooo light.... i put her on penicillin, next day i found her stuck in their pond, as she was so weak she could hardly walk... I have her shut away now, on penicillin, giving her lots of earthworms as she still loves them, and she's eating a bit of 16% layer ration, and vinager water. She was in a large run, with 4 other ducks, I have been feeding them, 16% layer ration, mixed with chopped grains, milk, and a bit of alfalfa powder sometimes... One thing that has changed in i've started feeding them, free choice oyster shell, of which they have been getting through lots of it... Do you think she could have eaten to much oyster shell?? She has very dark manure, and she also has like gloopy clear discharge kinda stuff (kinda like mucus), that often comes out of her rear as well......... I'm stuck with what to do with her the penicillin doesn't seem to be helping her, I've been giving her about 0.4ml once a day... Any ideas would be greatly appreciated!! Thanks for your time !