Carla, I  have a q or 2.  Was mom taking BC pills between births?  My
understanding is that if you stop BC pill and become pg breast changes may
not be very evident.  And this mom is a "proven" breastfeeder, right?  My
other understanding is that you  have to be severely underweight and have
really low intake to not be able to produce.  My anorexic mom who weighs 75
lbs when not pg, nursed without problem until  baby was about 8 mo old.
Then     she began to lose more and baby's weight gain slowed.  I've always
felt it was because she wasn't being as careful about her intake as when
the baby was new.

Also the fact that supplementation perked this baby and mom's supply right
up (increased stool and void, increased mom production, both in 24 hours)
would make me think that for whatever reason this baby had given up trying
and now that baby is enthused things will probably turn around very
quickly.  I do not think it was related to her lack of weight gain in pg.
Altho the 21 lb recent loss is a concern, I would think that adequate
nutrition at this point should fix mom up.  Someone with a low normal BMI
just isn't really starving.  Sincerely, Pat in SNJ