Can we ask about late/missed payments?

[Cameron Mertens]

Hello! My GF & I are first time landlords after purchasing our first triplex in LA. She owns her home we are currently in in Long beach as well. We are going to be moving into 1 unit of the triplex & renting out the other empty one, plus her long beach house. We have been talking applicants according to guidelines set from "The House Hacking Strategy" but I had a question about what we can ask in follow up questions to ensure we aren't doing anything wrong. An applicant meets our income requirements & our 600+ credit score but has a bunch of missed payments in the credit history, mostly on car payments. Can we ask for an explanation of this or is that overstepping our ability to inquire on things? Also, is this something we can reject the application over despite the other requirements being met? Thanks for any advice/insight/info, we are trying to make the best decisions but all of our current applicants have 1-2 question marks while meeting most requirements we have.