How to ask applicant for more details?

[Salvador Santolucito]

I used the BiggerPockets SmartMove application for the house I'm renting.  They applied and their income is a little below 3x.  I was expecting that the application would contain information about employment so that I could call and verify but the SmartMove application I got did not have any of those details... which feels a little lame.  When I went through Renters Warehouse in the past, the application had lots more details.

What is the etiquette for requesting more information?  Do I need to send them a form or can I just ask them over e-mail?  Since the income is so close I wanted to verify it with his employer.