Some if not most faded fish fade WITH their deep reds they usually had before peeling and are left with pink like yours. Unfortunately, they usually never become red and will remain pink in color.
First I would check your water parameters. If you are still doing the heavy water changes, that could be the main reason. Due to it, PH shock or not enough BB to make the ammonia and nitrite levels go up and hurt/kill your FH.
Or it could be simple things such as..... he was sleeping, you overfed him, or just feeling a little....lazy
Hope this helps,
JP