Obviously I do not know the specifics of this case, but being a loooooong time BT myself, let me give this bit of advice to BT parents…
Many times baalai teshuva are much more intense and fiery about their newly acquired frumkeit than a FFB. There is nothing wrong with that, but you must realize that your children are NOT you.
If they were born AFTER you became frum, and went to yeshiva with (mostly) FFB kids from FFB families, who, for better or worse, are more “use-to” a frum environment and more “moderate” in their frumkeit, than the “fiery” way you may be, your kids may find you to be fanatical.
Now I realize that YOU do not feel you are a fanatic, but it may seem that way to them. If you are are pushing (what seems at least to them to be) a higher than normal level of observance than they see among their friends, this may turn them away from observance completely.
This is even MORE the case if you became a BT when your kids were already pre-teens or teens. They may greatly resent the idea that just because YOU decided to change your way of life, that they have to also. Of course you want your kids to go in the Torah derech. The key to success is gentleness, s-l-o-w-n-e-s-s, and lots of love. Force will only push them away.