Etiquette question

I want to ask the BL readers here a writer-reader etiquette question. Several reviewers accepted my novels for reviews, but not all of them read the books (or wrote reviews). It's been a while. It seems most forgot about me. Should I keep quiet? Should I remind them about my books? Or is it bad taste from the reader's point of view? I don't want any reader to be unhappy with me, but they did accept free copies. As far as I understand, the unspoken agreement is that if you take a free copy from a writer, you read and review it. I certainly do that with every NetGalley book I am approved for. Or is it only for NetGalley?