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In a scenario like this, I've never heard of rent being included in the DTI. I've used 3 different mortgage softwares, and none of the programs count the current rent when calculating the DTI. Generally, the DTI is calculated by adding up everything that shows up in your credit report (all the monthly payments of installment debts and minimum payments of revolving debts), then adding the new mortgage & housing expenses (PITI+HOA), then dividing it by your gross monthly income. Does your rent show up on your credit report? I've seen thousands of credit reports and never once seen rent show up in them.
Without bringing this up, you can ask your LO what your DTI is and how it was calculated. Make sure that every tradeline is correct and also make sure that your monthly gross income is correct.