[somewhatshocked]

We have a seasoned, planted paludarium tank

What do you mean by "seasoned"? How was the tank cycled? How long did it take? How much ammonia could the tank process in a day? What ammonia source did you use?

Have you tested the tank to be sure there's no ammonia or nitrite present?

What's your water temperature?

was told the shrimp were younger

Young shrimp would be tiny. What you received are fully adult. Based on the photo, that particular shrimp appears to be quite old and near the end of its life cycle, despite the molting issue.

Any idea about how they were fed before you received them? Looks to me as if it's a combination of issues. The lower kH in your tank (which is why pH is 1.2 degrees lower) is the biggest factor, as it's tough for shrimp to adjust to softer water with less carbonate when they're larger adults. This is usually an issue if shrimp are received just before they're ready to molt but can still be an issue several weeks out. The other, smaller factor I suspect is a super-high protein diet from your shrimp source. Contrary to what some people suggest, shrimp don't need supplemental protein fed to them in high numbers - they get plenty from surface film, microfauna and regular shrimp food. But when fed high protein diets and kept in warmer water, as they often are by breeders and exporters, they grow faster. Combine that with water parameters they haven't been able to adjust to and molding issues like this occur.

Without knowing any of the other water parameters, I'd put this one on the seller and not you.

 

[somewhatshocked]

As long as the tank can process the waste created by your livestock (sounds like it can) and you don't detect ammonia or nitrate, there are no worries there. And since you have some kH in your water and a good gH, you're good there, as well.

As far as feeding goes, feeding every 2-3 days or so is great. Only feed what they can finish in an hour and remove leftovers. Try to alternate foods and incorporate things like zucchini, spinach, kale, stinging nettle. Spinach is great because you can wad it up into little balls and stick them in the freezer - no need to blanch. Just drop the frozen spinach into the tank. Though, admittedly, it's easier to deal with if you attach it to something for easy removal -- I like using fishing line tied to a flexible plant anchor. That's just in tanks where everything can't be eaten quickly. Some of my shrimp tanks can power through 4-5 spinach leaves in 20 minutes.

Still believe this is an issue with shrimp age, condition, health and parameters from the source and has little to nothing to do with your efforts, as you've handled things better than most shrimp newcomers. Unless you continue to see deaths/molting issues, I wouldn't worry much about it.