Crawfish - Anyone Cook Mushy Crawfish Before?

First, I want to let everyone know that I start using the two pots method to cook crawfish this season. I usually boil a sack for my family (mostly my wife and me eating as the kids are still small) We keep the leftoverrefrigerated and eat for our next 2 or 3 days. My wife eats it cold, while I would heat it in a pot with a little water to steam.

I boiled with this method 4 times this season and here is the result. Note that the soaking pot ingredients stay the same

1) No salt added to the boiling pot, just clean water - Great right after the boil and the leftover is still good to eat. The meat is still in great shape. It's not mushy or rubbery.

2) Same as 1.

3) Add 1 1/2 cup of salt to the boiling pot. Result is almost the same as 1 and 2. Just a little more cooked than 1 and 2, but still within the juicy meat and easy peeling range. Leftover were good too.

4) This is the one where the leftover is mushy and breaking apart. The crawfish was still good, and the meat was firm and juicy. Here are some key points:
a) Add 1 cup of salt and 1 cup of Louisiana Crab Boil to the boiling pot
b) Crawfish are not dead from what I see.
c) Crawfish are smaller and have thinner, redder shell than the 3 times before.

I cooked mushy crawfish once last season with 1 pot, and I chalked it to the crawfish itself. I didn’t overcook and soaked it for only 20 minutes. It was mushy fresh from the pot. I also note that it was the thinner, redder shell.
This time it gets mushy only after I refrigerated it. Is there something wrong with the crawfish themselves, but they were still alive and great fresh from the pot. Is it the salt and seasoning added to the boiling pot?
I will cook 3 or 4 sacks on Memorial Day weekend, so just want to understand what’s going on. I will probably go back to not add salt to the boiling water. I appreciate your time. Thanks.