None of my GALS eggs hatch. Are they duds?

I’ve been wanting to raise a new baby (yes I know I need to raise all of them and cull them accordingly) but I can’t seem to hatch the eggs.

I have a pair of fulicas. One is around 3 years old, the other is coming up on her first year…so maybe the younger one isn’t mature enough? She is big but still not as big as the older one.

They’ve been producing eggs but no where near the level I was told about. It’s maybe 10-15 a week? My bigger snail has laid a few eggs on and off through her life but has never self fertilized. I am yet to see the pair breed.

Of the eggs I find, they all seem to be duds. I’ve tried a few different things to try to hatch the eggs. Damp dirt of course, warm environment, isolating them into a cup or even just leaving them in the dirt to hatch naturally.

The eggs always end up turning a grey/brown and disintegrating. I have crushed/popped a few of them at varying ages and the shells always seem empty and full of water. Never actually seen anything remotely baby snail looking inside.

Snails are kept is a 170L tank that is 1/3 full of soil, lots of enrichment items like corkbark tubes and big branches, have constant access to cuttlebone, and eat a varied diet including but not limited to squash, bell pepper, broccoli, and dried freshwater shrimp for occasional protein supplement.

Thoughts?