Have you contacted the source from which you purchased the plant? It may have been diseased or at least your vendor may have been able to provide some guidance. These are tropical plants that are vulnerable to a number of pests. That said, it is not a plant with which we have any experience, and would advise you to read up on it here: https://hort.purdue.edu/newcrop/morton/soursop.html (Perdue is an excellent resource). We would also suggest that you contact the cooperative extension nearest you (chick on your state here: http://www.almanac.com/content/cooperative-extension-services ) If the folks at the extension do not have an answer they may very well refer you to a colleague at a service that is knowledgeable.
Have you contacted the source from which you purchased the plant? It may have been diseased or at least your vendor may have been able to provide some guidance. These are tropical plants that are vulnerable to a number of pests. That said, it is not a plant with which we have any experience, and would advise you to read up on it here: https://hort.purdue.edu/newcrop/morton/soursop.html (Perdue is an excellent resource). We would also suggest that you contact the cooperative extension nearest you (chick on your state here: http://www.almanac.com/content/cooperative-extension-services ) If the folks at the extension do not have an answer they may very well refer you to a colleague at a service that is knowledgeable.