Shrimp is it common..?

I have had similar problems in the past. Most recently I believed one particular piece of wood to be the culprit, though I'm not sure what about it was causing that same problem. I lost 20+ shrimp. I pulled the wood and did some heavy water changes for a few days and the problem stopped. I'd love to hear if any more experienced/knowledgeable shrimp keepers have a solid reason/explanation as to what can cause a shrimp to be stuck in its molt.

Well, as far as crustaceans are concerned... I used to have land hermit crabs, and whenever they had a hard time molting, it was because there was a lack of calcium in their diet. Granted, I don't know if this applies to shrimp, but it could also be that.

Yes it does poke it applies to most shrimp. Do a water change and check the ph and kh and gh and get sum fuval shrimp mineral supplement and seen if that helps in the future. And as far as shrimp what kind are they?

What does "too much new tap water" mean? I assume your tap is chlorinated - what sort of water treatment did you use?

I've done 90+% water changes in shrimp tanks in the past with no issues. Most folks say this is a bad idea, but if your tap and tank parameters are fairly close it shouldn't be an issue. Granted, my tap was unchlorinated at the time.

Shrimp tend to molt when water parameters change suddenly. I'm guessing you won't find anything out of the ordinary if you measure your GH, PH, KH. The next time you do a water change it might be helpful to measure these from the tank and from the tap to see what kind of difference these is. That could be your culprit.

Ah, well, it's probably a good idea to find out if you're chlorinated or not. You can do this with test strips or by contacting whoever supplies your water. Given that I got some hits for "superfund" in connection with Ft. Lewis water when I searched, it might be a good idea to use a water conditioner regularly to neutralize anything bad if you're on Ft. Lewis water.

It's probably also a good to pick up some test kits. An API GH/KH test kit is a $4.39 add-on item (have to buy $25 or more) from Amazon. I assume you already have a PH test kit, but you can get it with the API master test kit for $16 on Amazon.

GH and KH are one of those things that if you're not actively trying to change them you probably won't use the test kit much at all, but it can be helpful to get a baseline.

According to this:

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your water is indeed chlorinated, so that may have upset your shrimp a bit.  

I'm new to chlorine myself as I just got switched over to City of Lacey water from an un-chlorinated community well a little over a week ago.  I've done one water change in that time (50% on 10 tanks) and used prime in all tanks with no issues apart from all of my snails making a run for the waterline at first.  They usually don't do that... but they seem fine now.