This is the 13889th most frequent Russian word.
обнаружились
"Обнаружились" means "were discovered" or "were revealed."
In this sentence, 'обнаружились' is used to denote the discovery of streaks on the ceiling that became evident.
После дождя обнаружились потеки на потолке.
After the rain, streaks on the ceiling appeared.
In this case, 'обнаружились' highlights the realization of missing items during a process or activity.
При разгрузке коробок обнаружились недостающие предметы.
Missing items appeared during the unloading of boxes.
Here, 'обнаружились' conveys the finding of faces in the photographs that had not been noticed before.