It asks for 6 products with minimum cure rating of B+. When I got to 6 cures with minimum of B+, it didnt say I won. I was using 4 lv1 and 2 lv2 cures, so I though maybe it wanted 6 cures from different trees. So I did that as well, 6 B+ cures from 6 different trees. But it still didnt count.
Here is the link to the screenshots http://imgur.com/a/mazcW