I had this problem too, and this won't solve the problem but I found the revitilising stew helped.

It is a pain but I'd just heal everyone (if they got sick because they were starving) then make the stew. It just means you are less likely to lose people because they are starving as the stew completely fills up their health bar. In the meantime, I'd have as many on tech as possible and not worry to much about what they farmed.
In effect it was: as many people on tech as possible while people starved. Come back, heal and serve stew. Repeat until food problem solved.

Like I said, I can't solve the problem but this did help in the meantime for me.

PM me if you want to know what the stew is or you can find it on posts.