I think there is no problem as the contents, you mentioned, almost similar. I think that increases the probability of getting traffics on all three sites.
I would not be promoting 3 sites on a single article unless the sites are all about the same subject.
I am also a SEO Service provider as well SEO Training In Delhi. I usually submit 1 article in 30 sites. In a day i post 7 articles means 1 article in 30 article directories and the result is i am at top in Google search result with the keyword SEO Outsourcing.
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