i think i played around with the stacked bars when i first tried this chart but i think given the scale on the y axis if one of the users with a lower total referrals stats (e.g 74) add 1 new user this week then the stacked bar for that 1 referral is barely visible, also in that case there is not space for the label to sit within the bar area.
I will play around with it again this week and see how it looks.
Thanks :)