Soft gummies can be a result of multiple variables. It’s best to start by first ensuring you hit your target setting parameters, brix and pH. You want to end the cooking procedure between 75-84% brix with a final pH between 3.0 and 3.5. The brix cannot end below 75% or the gel will fail to set firm enough to pull from the molds. If the final pH is above 3.5, the batch is lacking the necessary available acids required to form a gel and you will want to increase the citric acid usage on the next batch.
Low pectin usage and or a long cooking procedure can result in a soft gummy. Cooking procedures that are over an hour from beginning to end will likely have an increased pectin usage.