I have a question about a gap in my teeth which i have noticed to be visible all of a sudden!

I've never had a problem with my teeth & i've been wear a night guard ( plastic retainer) that my dentist gave me to prevent grinding in my teeth. Recently i have also tried teeth whitening with mouth trays. Initially i didnt have a problem but now i've noticed a gap in my teeth all of a sudden! Can it be from the teeth whitening ? Or the retainer? Im really worried & nkw i dont have a perfect smile.

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