If menstrul cycle is fine , does there mean there's a condition causing low feritin in a female?

Not necessarily: Ferritin levels can be related to blood loss but they can also be effected by dietary iron intake and that is not necessarily a condition, it can simply be a matter of food preferences.

Iron deficiency: If your menstrual bleeding is heavy enough to cause iron deficiency, this would cause low ferritin, a marker (or indicator) for iron deficiency anemia. Hope that helps.