Hi Melach sorry something happened to my messages. They joined somehow. I couldn't edit it.
Well the scripture I would use is-
Revelation 2:5 New International Version (NIV)
5 Consider how far you have "fallen"! Repent and do the things you did at first. If you do not repent, I will come to you and remove your lampstand from its place.
Notice the word word "fallen" is also in this scripture.
1 Timothy 4:1
Now the Spirit expressly says that in later times some will ......depart....... from the faith by devoting themselves to deceitful spirits and teachings of demons,
*Its possible to depart from the faith as shown above.
And yes "some" were not saved to begin with. But "some" were of the faith.
1 John 2:19 New International Version (NIV)
19 They went out from us, but they did not really belong to us. For if they had belonged to us, they would have remained with us; but their going showed that none of them belonged to us.
*Just because 1 john 2:19 exists we cant pretend 1 Timothy 4:1 Doesnt exist. Then it makes a one sided gospel. And only part truth... according to the bible.
Thanks