The trio - Christina, Rachel and Ivette - were seen making it into the final 24 on Saturday.
But it has now emerged that one of the girls is under 16, the show's age limit.
Mentor Louis Walsh, 57, will be seen breaking the news to Tru Colourz on this week's show.
'They're devastated,' a source tells the Daily Mirror.
'Louis has the agonising task of telling the girls they can't continue this year but he softens the blow by suggesting they can try again next year when they are old enough.'
Harmony Hood will replace Tru Colourz.
Where to next?
- Familiar faces on X Factor
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- X Factor contestants