Sourcing for past 2 stories

Looking back, there were a lot of things I could have done different in my last 2 stories. In the last story I wrote about unrecognized fraternities, I realized I did not speak to the right people. Originally I had a person in mind who would have been perfect for the interview, but he was sick all the days I had available. Because of this, I should have honestly redone the whole story. Instead I attempted to do the same story with different sources, which I now realize did not make sense. Midway through the story, I pretty much switched topics, something that is never allowed. While I should have definitely used different sources in that story, I feel that the sources in my first story were very well chosen. I did a story about scope, and got interviews with 2 new members, and an older member who was also a director. I felt that the combination of these three people gave a great insight to my story topic, which was the comeback of scope. Getting sources is completely new to me, and I am still learning. However I feel that I am getting better and hopefully I will be able to know what the perfect source is for a certain story.