While wine or cider is fermenting, it is not unusual for some solids to settle to the bottom of the fermentation container. This stuff is mostly small bits of fruit and dead yeast. This is normal and nothing to worry about.
Here is what a five-gallon carboy of hard apple cider in my basement looked like after two months.
Siphoning the wine or cider from one container into another is an easy way to remove the sediment at the bottom.