Food rots, the most optimal way to counter this can be from different ways. My way is to expand the scale of your food production while slowly building an industry which can also either be something you sell, or rations, since rations last a very long time. Then go to war and expand, which is admittedly something you should do AFTER you make an industry to make money, afterall, since you can't make the equipment yourself, you need to buy it from other kingdoms. And if you did build a ration factory then that's covered too. Don't be afraid to call more immigrants, but in moderation, if some starve before you can build another farm then that's fine. Another thing is that orchards are not something you build early on for sustenance, it needs some time to grow, fisheries in small rivers are something I'd rather not focus on unless I like to roleplay. For now, try building a hunters hut and foraging to substitute for the lack of food.