Those must be some huge plants and a lot of "medicine" for only four people.
24 plants x 1.5 lbs. per plant = 36 lbs.
1 lb. = 438 gm
36 lbs. x 438 = 15,768 gm
1 "dose" = ~0.25 gm
15,578 gm / .25 gm = 62,312 doses
4 people x 365 days = 1,460 person-days
63,312 doses / 1,460 person-days = 43.4 doses per day
That oughta do it.