Chrome window shrinks on Mac Air after switching apps

My chrome screen keeps shrinking since new the new update. I have a Mac Air and had to reinstall all my apps after a service. Since its been back, everytime i move to another app and go back to Chrome it has shrunk. It is a silly thing but irritating having to keep widening it up again. I changed the settings on the apple settings for display and tried on chrome. Any ideas on fixing this would be appreciated. Thanks