Medical Bills on Credit Report

I have  a credit question. I have three outstanding
medical bills on my report.  They total about $800. Would it be in my
favor to pay off the debts right away, or should I pay them off one at
a time?  I have read that it can hurt my score by paying these off.
Also, is there anything I need to tell these creditors in particular
pertaining to improving my credit score?  Any advice would help.
Thank you

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