There are a few reasons pickled jalapeños turn mushy. First, be sure you are only using freshly picked jalapeno peppers that are free from any soft or dark spots. Second, if you are using a water bath or pressure canner to make the pickled jalapenos, that will cook the peppers and make them soft. Instead, try a refrigerated pickled jalapenos recipe. It uses a hot pickling mixture over the fresh jalapenos but then goes into the fridge to sit for a few days. This pickling method keeps the jalapenos crisp.