hi, think I've seen info related to this topic before but can't find it in the search... what is the difference between level 1 vs. level 2 formula & is it necessary to go to the next level? my baby is 8 mos & drinking NAN HA, our ped just suggested that we try level 2, however i've also been told many stay on level 1 & this was also recommended by my lactation consultant. any advice apprec, tks!