I've read that peahens only need 1 1/2% to 3% calcium in their diet, much more and it is hard on the birds and especially the cocks. That is why the oyster shell is better to offer them than making the cocks eat high amounts of calcium in the feed. Kathy is quite right about the need for a proper balance in the feed but be careful to not cause an imbalance with too much of any one thing.
I have a breeding pen with eight hens and two cocks that recently laid a very thin shelled egg, it broke in the nest box when another egg fell on it while being laid. I too was surprised to see how much of the oyster shell disappeared in the two weeks that followed.
In your case you need to take more drastic action with the hen laying soft eggs if you can catch just her and maybe put her in a small cage for easy dosing for a few days. I think that you have done a good job with what you are doing and you should see hard-shelled eggs in no time.
I have a breeding pen with eight hens and two cocks that recently laid a very thin shelled egg, it broke in the nest box when another egg fell on it while being laid. I too was surprised to see how much of the oyster shell disappeared in the two weeks that followed.
In your case you need to take more drastic action with the hen laying soft eggs if you can catch just her and maybe put her in a small cage for easy dosing for a few days. I think that you have done a good job with what you are doing and you should see hard-shelled eggs in no time.