When you have a strategic plan, your first action is to work out why those numbers changed. Do the needs of this new traffic source differ from your established sources? If so, how? These questions are then followed by tests that attempt to answer them or, at the very least, help determine which tests to run next.
When you implement a conversion strategy, you should do so understanding that a single tweak won’t fix all your conversion problems. You should be prepared for results not to support your original hypothesis. The knowledge you gain from testing it, contributes to growing an understanding of how you can serve your customers better.