I am not sure what type of bin you're using but that really doesn't make much of a difference.
Some bins may create more muddy leachate than others. sometimes It can depend on the screening at the bottom of the bin.
Is it a plastic bin with small drilled holes or a flow through type worm tower like the Worm Factory?
Anyway, this is usually nothing to worry about as worms tend to be the cause for muddy leachate at the bottom of worm bins.
The watery substance will mix in with the worm castings and they will wriggle around and crawl all over the bottom mixing everything up quite nicely.
As long as you don't have too many worms down there and it doesn't smell too fowl then I think you are okay.
If you have a lot of muddy drain off and a lot of worms crawling around then something is wrong with the worm bin system. You will need to do a little investigating.
All bins, however, will sometimes have this muddy substance depending on how wet or how high the worm tower/worm flow through system is.
Thanks for posting your question,
Pauly, The Worm Whisperer