All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
May Allah reward you with goodness for your concern about the upbringing of your children, their memorization of the Quran, and your diligence in preventing them from indecency and its causes. May Allah place that in the balance of your good deeds, facilitate for you their good upbringing, and grant you satisfaction with their actions.
Firstly, it is undeniable that supplication is among the most significant means through which a Muslim achieves what he seeks. One of the names of Allah, the Most High, is Al-Mujeeb, and He responds to supplication. The supplication of parents for their children is accepted, as established in the authentic Sunnah.
Secondly, psychological calm is important when dealing with such behaviors from them. This aids in providing good guidance and dealing with the situation properly, as opposed to reacting with nervousness. At the same time, there should be a form of firmness in guidance, so they realize the seriousness of their actions and understand it as a gateway to immorality.
Thirdly, remind them of the blessing bestowed upon them by Allah the Almighty in memorizing the Quran. It is a blessing deserving gratitude, and one way to express gratitude is through obedience to the Most Merciful and refraining from disobedience.
Fourthly, remind them to be aware that Allah is watching, that He knows all of their words and actions. They are assigned angels who record their deeds, both good and bad, and all of this is documented in a book that does not leave anything, small or large, without being accounted for.
Fifthly, strive to know who they associate with, encourage them to be in the company of the righteous, and caution them against bad companionship. Connect them with trustworthy individuals associated with centers where righteous people gather, filling their leisure time with lawful and enjoyable activities, and teaching them matters related to their faith.
Allah knows best.