Help on YELP!

[MomNeedsVacay]

so, I work at a private fitness studio that opened a few months ago. On Yelp, almost all of the reviews are great, glowing reviews....one person (or two---can't tell if its the same person using different alias') is writing the most horrible things; i.e. "I heard the owner of the studio slept with investors (some married) to get it up and running" ..."I heard the owner also brings home male clients from the studio and does who knows what with them" ..."The owner of the studio pawns off her 4 year old daughter so she can "service" her clients"---"THe owner's 4 year old daughter doesn't smile because her mother has put pressure on her appearances" ---I am sure these things can't be true about my boss... even if they were true, though....what do these things have to do with the business itself??
My boss got the reviews initially taken down by Yelp---but now they are back up--- this person keeps reposting... Is there any legal action that can be taken? Defamation of character?? I think its awful that they talk about my bosses' child as well....any advice?