I'm stuck with the tasks "Have 50 survivors living in your camp". I already max and upgraded everything...

I'm stuck with the tasks "Have 50 survivors living in your camp". I already max and upgraded everything. I cannot complete the task due to multiple unassigned or worker died due to starvation. My food production only 49.7 and the cost of the meal is 1200. The reason why I have a low production of food, because I don't have the specific hero for it. I opened a lot of chest but still the hero for this level still not get. I understand that we cannot get the hero we want when we open the chest, but I already max the level of all the production and the dorms, but still I don't get the hero yet.