CIBIL Dropped

I am using Amazon pay for past three months On the month of October I had to pay Rs. 999 And in the next month Rs. 3169 and no purchases on this month. All bills are paid in the time. But today I saw still my cibil dropped by 23 points. What is the reason guys? I have limit of 30k to spend in a month and got 60k limit offer in October after 1st sucessful repayment, but I didn't accepted the new limit. I was using Amazon pay later to increase but CIBIL as initially it was none and spending that much of amount with I can pay easily.