No, Alex wasn't highly rated. On the "family history" that CD sent LV on 10/30/18, Alex was 2L, while everyone else in LV's family of origin was 3L (except CD had rated LV 4.3L and had indicated that those sisters who had died - one an infant and the other a married mom - had graduated to 4.1L).
Here's a link to the story that contains the "family history" documents CD sent LV by email:
Documents sent by Chad Daybell reveal so-called 'past lives' of Lori Vallow
Since the whole rating system was such a pile of complete horse manure, my guess is that Alex became dark when he was up to his chin in it and CD and LV felt they might sink to that condition as well.