Solutions for clothing that appears stained after it is wet

I bought this jumpsuit and I absolutely adore it but unfortunately any spots of water dry darker than the rest of the jumpsuit making it appear dirty. I reached out to the company and they refunded my money but I am wondering if anyone has any tricks on how I can treat this fabric. It is made from:

• 3% Elastane
• 41% Cotton
• 56% Lyocell

I was thinking of using scotch guard but I know the internet is full of smart people so I wanted to reach out.

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Thanks so much for any advice!