Actually... the concept that it "sometimes takes a while to get it right" doesn't really hold much water anymore. I'd be willing to bet your problem is with supplementation. Ventrimaculata/Amazonica are notorious for throwing bad eggs when they don't have proper supplementation.

What is your current supplementation routine? Are you providing them with a source of preformed Vitamin A like Repashy Vitamin A+?

If not, you should be rotating Vit A in with your feedings 1-2x per month. (not more frequently, as you can overdose them with it)

When I was breeding amazonica years ago... they stopped laying bad eggs and I stopped getting froglets with SLS as soon as I started the parents on a supplement rotation with Vitamin A.

Hope that helps... and good luck!