I'm assuming you mean the shells are getting thinner. Here are some alternate food sources of calcium.
Imp- I occasionally sprinkle powdered milk on the feed.
1.Spinach
2.Turnip greens
3.Mustard greens
4.Collard greens
5.Blackstrap molasses
6.Swiss chard
7.Yogurt
8.Kale
9.Mozzarella cheese
10.Milk (goat's milk and cow's milk)
11.Basil, thyme, dill seed, cinnamon, and peppermint leaves
12.Romaine lettuce
13.Rhubarb
14.
15.Broccoli
16.Sesame seeds
17.Fennel
18.Cabbage
19.Summer squash
20.Green beans
21.Garlic
22.Tofu
23.Brussel sprouts
24.Oranges
25.Asparagus
26.Crimini mushrooms