The 1841 census has :-

John Mylrea 50 Tailor Ballachurry
Elizabeth 40
James 20
Ann 5 (Mary Ann)
John 3
Margaret 1m.

IGI adds Catherine 1821 Jane 1825 Elizabeth 1827 and 1830 Susan 1832.

Susan is in the burial register 1837 and it looks like Elizabeth 1830 is living with John and Margaret Radcliffe also at Ballachurry.
Jane and Catherine may be working away.

The repeat name for Elizabeth brings you back to the advice from Sue and gives the impression that you need to look elsewhere for your John 1823.

Len Faragher