I have 3 villagers that I train to healing: Manuel, 60 y.o, adept doctor very near to become master; Bénédicte (she is my runner) and Paula, the youngest, whom healing is the only skill. And I absolutely want that they become Master Doctor! So I bring them to study the strange plants... but, oups! Manuel makes a baby to Paula and she is "out" for a long time! Then a villager rings the Gong and it takes health! Yippee! I bring quickly Manuel to heal sick villagers but... Bénédicte is already here! I bring him to another one but...she is already here! And Manuel cannot improve his skill! And what a frustration!
The moral is: 1°: take care when you put a male and a female on the same task!
2°: some time, the runners are a little bit annoying! especialy for the other healers

PS: one hour later, studying strange plants, Manuel is Master Doctor!!