Problems with mold and product longevity

Greetings

I am a producer of traditional biscuits made in my country, they consist of a soft dough with about 16% water and 4% fat, a mixture of 2% sunflower oil and 2% palm oil and a layer of fondant on top. All production is traditional and handmade. We do not use any technological systems. I wanted your help to solve the mold problem in the product as I currently do the production in a traditional way and do not use additives. The longevity of my product depends a lot on atmospheric conditions. During summer season the product endures from 4-6 weeks, while during the winter maximum 8 weeks after and if there is no mold it loses its taste and strengthens. I really need your help to make the product durable for at least 6 months to resist mold as well to preserve softness and taste.

I want to emphasize that I have a problem with mold both in the dough and in the fondant.

I would greatly appreciate your advice.

Thank you.