Mystery snail sick?

[TO KYO]

My mystery snails be growing and dropping out this weird jelly slime everywhere. Is this fungus or something?

 

[Colin_T]

It's probably just mucous. Make sure the water quality is good and do a big water change and gravel clean the substrate if there is any ammonia or nitrite readings, or a nitrate level above 20ppm.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.