Did you have help holding her down to look for the vent? It took me a lot of digging to find my girl's. I thought I'd never find it but she was being still and not making a fuss so I just kept at it. I have never been able to "feel" for an egg on my girls but I've never had to stick my finger in the vent either. When they've been egg bound that calcium gluconate works like a charm.Right! I looked and looked and couldn't find it. Thankfully I didn't have to worry about it this time. She's continued to be fine. But I've found a few other soft shell eggs since, including one today. But I also got 3 eggs today, including the soft one, so that means all 3 of my ducks are laying. I'm guessing they are each laying soft eggs because its the beginning of the season. IDK. I've had soft shell eggs before, but I don't recall it being clumped at the beginning of the season like this. I've put out oyster shell for them, but I'd been putting it in their food. There is plenty laying around, so I don't know if they simply choose not to eat it or what. And since I put it in a bowl, which is getting eaten slowly, I wonder if its just going to take a while.
Good suggestion on they dye. If I can ever find a vent when need-be.
Have you tried crushing up calcium citrate pills and giving it to them? You may want to try that which should help with getting the shells hard. I have always had oyster shells out for my girls but yet sometimes I get soft shells too. Since 6 of mine have not really stopped laying since they began their shells are getting much thinner now. The 2 young ones's shells are nice and thick though. I really need to start doing the calcium citrate myself.