Bleeding is very, very rare. It happens when something that looks like blood shows up visibly in a candle that should have no blood or substance that looks like blood in it.
This indicates that a spiritual entity or attachment has been attacked and badly hurt and/or destroyed by this spell.
It is most common in cleansing work and indicates that the cleansing has removed a spiritual attachment and/or a spiritual entity that was hostile or had ill intent in some other way.
It also often specifically indicates that someone has put a sexual control spell on the target of the work and that the spell had broken the spirit or energy that was causing that control spell to work.
What To Do:
You should absolutely get a reading from a reliable, probably professional, reader who knows about spiritual entities and/or conjure work. This sign is rare and almost never positive. It usually means someone has done heavy conjure work or other spiritual binding on the target of the spell.