Battling rubber eggs, how long to see difference after making changes?

[Ciqala]

In the last month or so, I've had a few hens {out of a flock of 18} laying rubber eggs... 1 1/2 yr old adult leghorn, a 4-5 mth old leghorn and 5-6 mth old red sex linked. When I bring them inside and give them yogurt with a crumbled 1/2 tums on it they straighten out. They get Blue Seal layer feed with free choice oyster shell, a treat of some sort in the afternoons.

Before getting chicks this past Spring, I use to feed Dumor's layer pellets. I only switched foods when they all got old enough for my own convenience. This past Friday I went back to using Dumor since I never had a problem once with rubber eggs while using it, I also started putting a bit of oyster shell in with their feed before I wet it down. Yesterday I got three rubber eggs again, today I picked up Calf Manna Performance Supplement and started them on that.

My question is - how long would it approximately take for me to see a difference if these changes I've made in their diet are working?

 

[katelk]

What do you mean by wetting their food down?
Also, young hens may lay goofy eggs of all sorts pretty regularly. How many normal eggs are they giving compared to rubber eggs?
When making diet changes, you would probably see egg results within a week I would imagine. I am just thinking from experience when I have neglected to refill my oyster shell feeder and then remembered it once I noticed rubber eggs or thin shells.