out of 3 pool member 1 member is up

I assume this is related to your health monitors failing question?

So you made a custom monitor and assigned the same monitor to 3 pool members separately? What version of BIG-IP are you using? Check to see if a different monitor is assigned to the whole pool as well.

HERE, HERE, and HERE are some good articles to read up on.

Hope that helps! If it does please up-vote and select this answer, it'd be greatly appreciated!

-Dylan