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Did you get the pre-approval after you got the card in April? Assuming that you had the card and it was reporting to the credit bureaus, the lender would've looked through your credit report and rolled all of that into the DTI.
I'm new in the process so I'm no expert, but every lender I spoke with indicated that unless you have credit decline, income loss, or something of that nature, you should be good for final approval. So defintely don't seek any more credit.
Basically, as long as the lender was aware of your collection and late payment and new card prior to giving the pre-approval, you should be good assuming you stay on track.
Most likely they did see it, but for peace of mind you might just want to reach out to them to verify.