Tax code change to 1150L

I started a new job in April this year, and have received regular payslips. I have noticed that my in weekly payslip, my tax code has changed from 1275L to 1150L. I have not received any benefits and my wage has not changed. The only deduction to my payslip is my student loan. Why has my personal allowance decreased?

Hi,
We will need to access your record to review this for you. You can contact our Income Tax team below.
Income Tax: general enquiries
Thank you.