I make marshmallows as a self employment.Normally I make the stuff packet them and send to the market.But unfortunately in about 7 days time this gets some fungus or sometimes it starts melting. I am in a big problem. Please help me to avoid this . And please tell me how to improve the quality of this. I use sugar, gelatin , liquide glucose, cream of tarter and citric acid to preapre this. thank you in advance.

I hope you have a health clearance and sales license to sell your product.

Apparently you have an ingredient or mixture in your recipe that is not room temperature stable. There are numerous recipes for homemade Marshmallows on the Internet so I would suggest comparing your recipe to theirs and see where the differences are and try adjusting your recipe accordingly.