WL
I've never tried herbs, but I can tell you how to enlarge them about half a cup size without taking anything.
The breast has 2 biofeedback systems during lactation.
a)the actual mechanical action of suckling
b)the emptying of the ducts during the nursing of an infant.
So when the nipple is suckled, this sends the feedback to prepare the ducts for further milk preparation, so they enlarge in preparation, resulting in a slight breast enlargement. This was in my human physiology lecture about 10 years ago.
Boyfriend and I tried this out, boy did it work. 5 min of suckling of each breast 3-4 times a week resulted in half a cup increase. I'm a 34B/C. Taper off the suckling, the ducts go back to normal size and breast reduces back to prior size.
No herbs, no drugs, no surgery.