High altitude baking requires some nuancing. A good rule of thumb is to use less yeast or leavening agent since less is more at high altitude due a decrease in air pressure. Other general rules are to decrease fats by 1 or 2 TBL especially when making high fat cakes. Reducing every cup of sugar by 1 to 3 TBL also can help. Finally increasing liquids by a TBL at a time will also assist in your final results. Since Bella Gluten-Free is itself at high altitude, most of the recipes have been adjusted for proper baking for all altitudes.  If you are 6000 ft or higher, and are using Bella Gluten-Free Bread Mixes, however, follow the instructions on the package for high altitude for best results.