how long until oyster shell works?

[frankenchick]

Two of my girls laid soft eggs today, the kind that feel like deflated balloons. At least I think there were two eggs -- someone ate all but the outsides.

How long after I start feeding them the oyster shell will the eggs get hard?

 

[speckledhen]

Is it really hot where you are? That also causes bad shell quality, the heat stress. I'm having egg issues with my girls for the first time ever during this awful heatwave and may lose one because she laid egg contents without shell or membrane and it's still inside her somewhere. I feel awful because I've never lost a chicken to illness or a predator and she's one of my favorites.