The spread of problem residential borrowers is becoming more concentrated in Queensland and New South Wales, while the incidence of stressed borrowers in "hot spots" is getting a little worse.Fitch Ratings yesterday released an occasional report on mortgage delinquency in Australia by postcode.Nelson Bay, north of Newcastle, remains the suburb with the most troubled borrowers. Fitch said 7.8 per cent of loans to borrowers in the suburb were 30 days or more in arrears (measured by value) up from 5.6 per cent a year ago.Other hot spots include Budgewoi, on the NSW Central Coast, Eagle Vale (near Campbelltown), Hoxton Park (near Liverpool) and Surfers Paradise. The latter suburb did not feature in Fitch's tables last year.No localities in Victoria rated a mention in the Fitch report, so borrowers in Melton (in Melbourne's north-west) have by and large caught up with loan repayments.