Conditional format formula to highlight cells with a percentage

i have set up conditioning formatting to highlight cells in a row yellow if they are 3 or under. I have also added another rule to colour the cells white if blank so it will only colour cells within the table. However, the columns with the weekly percentages are being affected as they are being read as below 4. Can you please give me a formula to recognise a cell with a percentage format and to colour it white thus removing the yellow highlight?
Thanks.