Let's all think positive thoughts!
I think acclimation is always the key. Once you get them adjusted and eating they stand a good chance of surviving, especially considering you already have naturally soft water. That's probably going to be really helpful. Most people who get the little ones report velvet or a velvet-like disease that usually occurs within a few weeks of import, then they just start crashing. It's similar to importing young altum angels which clamp up and die off in large numbers. Constant parameters, warm, clean water, and getting them eating will go a long way into putting you ahead of the curve.