How large are the sevs? If they are 5"+, you could very well have a breeding pair on your hands. Pay attention for lip locking (aka kissing), shimmying (don't know the proper term, but its where they swim next to each other facing opposite directions and kind of wiggle against each other), fiercely defending a spot in the tank, and/or sometimes grooming each other. These are all signs of a breeding pair about to spawn. If this is the case, those sevs think the whole tank is theirs and anyone else n it are intruders. They will aggressively defend their young from anything they believe to be a threat.