You'll improve
Part of the whole program is getting you to realize how your whole body works together to develop strength and stability. (and why free & olympic weights are better than machines!) Wider stance helps, as someone mentioned above. Maybe you're stepping your front foot out too far as well. My recommendation - nail the form down before you add weights. Maybe put your hands out in front of you when you do the lunges, to help with balance.
This may be something fun to do... Bookmark this page and come back to this thread when you finish stage 4. It might be a really good way to realize how much progress you've made since your original post in the thread, in just a matter of weeks.