Is my fiddler crab dead or molting? Should I leave it in there?

I had one male fiddler crab for the last couple months. A few weeks ago I got 2 females. One female was a little bigger, the same size as my male and the other female was probably half the size. The smaller one was lively and normal yesterday and I think this morning it was moving. Today I noticed she was not moving. Another female crab walked right on top of her and she didnt even care. I took her out and she didnt move. A little bit of white liquid came out from her. I wasnt sure if it was pee or water or what. I read a little bit about molting and it sounds like its possible she could be molting so I put her back in to leave her alone. So is there an expert out there that knows if she is molting or dead? And if I leave her in there with the other 2 crabs to see if she's molting and she's actually dead will her dead body be harmful to my other crabs? Please let me know thanks.