That was also my polite way of saying, without being a jerk, that someone shipped adult shrimp - a bit of a rip-off, in my opinion - instead of juveniles. Many sellers ship adults because their lines aren't as 'pure' as they claim (or they're unproven imports being offered as anything but) and most buyers are unsuspecting. They tend to be less healthy than experienced hobbyist-raised shrimp and can't handle slight parameter swings, in part, because they're less healthy.
And... it can also be tough to tell how old an adult shrimp is. It could be near the end of its lifespan when you get it and look similar to a relatively 'young' adult. Which is a bit of a rip-off and frustration even if someone is buying adults because they're breeding age.
One of the reasons older shrimp have more difficulty adjusting to variances in parameters than juvenile shrimp is because they aren't growing and molting frequently like a juvenile would. Juvie shells are constantly growing and re-hardening and that means they're able to better adapt to osmotic pressure variances.
If you're having better luck with adults than juvies and you're pretty sure they're healthy, something is definitely off with the tank. Could be microbial, pathogenic, could be slight ammonia levels you aren't detecting, a bazillion different issues. Could even be something some of your substrate or hardscape is releasing occasionally.
As far as one tank exploding and one not... that's not something I've ever really had happen unless there's something haywire with a tank. Though, when it comes to Caridina, I've had tanks that won't produce as much as another if it's a degree off temperature-wise. Being a foot or two higher or lower on a tank stand can lead to those differences. And if the tank is larger than a gallon or two, then there are more likely to be different temperature regions of a tank. Wouldn't matter for hardy fish but might when it comes to shrimp reproduction. Nothing to worry about, really, just something that could help explain what's going on.
touched on something kind of important. I don't want to go too far into it, lest some buttcramps here and there complain that I'm promoting something I sell (to be clear - I'm not promoting anything because I don't make mass quantities of anything)... but... quality of ingredients matters a heck of a lot more for sensitive critters than some can imagine. It's why I steer clear of mass-produced shrimp food that doesn't have any sort of quality control on the ingredient growth front. I'm not saying mass-marketed foods aren't good - I'm saying people need to be picky about what they buy when it comes to feeding expensive critters. I've had such negative experiences in the past that I won't include an ingredient in something I'm feeding my shrimp if it wasn't grown entirely by me.
I got burned enough 12-15 years ago that I even started growing my own Terminalia catappa in a greenhouse environment. For anyone interested in growing their own: they do pretty well in containers, are easy to trim and supplemental lighting is cheap these days. Hardest part is getting them to sprout.