Have employee on paternity leave who wants to come in and discuss issues with her pay-should I address now or wait until they return from their leave? I'm thinking paternity leave is designed to get away and stay away from work stress not come in and discuss issues that can wait.

Not an expert on this at all, but the employees I know who have been on paternity/maternity leave generally don't come into the office to discuss financial compensation.

If they are on FMLA, I would steer clear of any workplace discussions with the employee until they return.

they need to have the conversation with HR, you may not have any work conversation with them when they are on FMLA, even if they start it...

Agreed, general conversations about work shouldn't be had while on FMLA. The only thing that should be discussed would be facilitating return to work, but even that is preferable to go to HR.