I had zoom whitening done 2 weeks ago. After the process my teeth got to whitest level on the chart, I was really happy but now

It's been 2weeks, & my zoom results have completely gone away. I brush 3 times ATLEAST a day. Sometimes up to 7. I still have been staying away from coffee, tea,and other colors tainting food/drink. I am so bummed. I knew they wouldn't stay as vibrant but I am back to the dull yellow color. (My teeth weren't bad before zoom, I believe they said I was about a 4 on the scale), I have used the whitening kit they sent me home w 4 times already. What can I do? They did a 1 time 1 hour session on me.

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