There are many reasons why a score may change. FICO® Scores are calculated each time they are requested, taking into consideration the information that is in your credit file from a consumer reporting agency at that time.
So, as the information in your credit file at that CRA changes, FICO® Scores can also change.
Review your key score factors, which explain what factors from your credit report most affected a score.
Comparing key score factors from the two different time periods can help identify causes for a change in a FICO® Score.
Keep in mind that certain events such as late payments or bankruptcy can lower FICO® Scores quickly.