I'll leave the morph identity up to someone else, but as for size I just asked the same question a few days ago
I have an 18month old corn (2 in July) that weighed 32grams when I got her jan 9th. I weighed her a few days ago and she is now 53grams. Still smaller than most corn's that age, but from what I've been told it's really nothing to worry about, as long as they eat.
Yours are drinking and look healthy ( to me, a beginner) regardless, I think chucking the old pinkies was a good idea and maybe try stepping up a size after their first feed? I am feeding my corn rat pinkies for now, which have a higher fat content, for a few more feeds then I'll be switching over to hoppers and hope that helps her grow
Good luck, I really like the look of the female, whatever she is!