No, you should not change percentages at this point. You have taken expenses and depreciation based on a certain percentage. You have reaped that benefit for 3.5 years.
However, you can go back and amend your prior year returns to adjust the square footage to reflect the more accurate percentage. Once you have made the corrections and paid back any deduction you were not entitled to, then your 2019 return will be in alignment.
Generally, you must file Form 1040X within three years from the date you filed your original tax return or within two years of the date you paid the tax, whichever is later.
