The Fenugreek may be a confounder here.
Is the blood bright red or dark black and tarry?
If it's bright red it is from low in the intestinal tract usually the rectum.
I can't see how the Fenugreek would cause that type of bleeding.  I would
suspect a rectal tear.
Perhaps the lack of weight gain isn't entirely related to the baby's intake
either.  Remember that when babies are trying to heal themselves they burn
more calories and hence do not gain weight.
I think it is important to remember that not all *Feeding Problems* are
feeding problems.  I have had too many (far too many) cases where
breastfeeding was blamed and then the true source was discovered.  Everything
from  inborn errors in metabolism (one fatal), to botulism, to urinary tract
infections  to intestinal parasites in a 7 week old.
Marie Davis RN IBCLC