Larry this has been happening to me as well.
In April, I downloaded and installed the Mini Clip 8 Ball Pool update.
I was at 350,000 coins. Now I am at 150,000 after winning tournaments, completing challenges and winning games.
All coin growth has stopped. I filled out at least ten request forms on their website with no reply related to my problem.
Write down the time you start the game - if coins go missing record how many.
They will have to do something if people report it.
I am looking for email addresses and intend to report them to PayPal.
Terry