Lenders in the LendingTree Network saw rates on 30- and 15-year, fixed-rate mortgages plunge to a six-month low this past week, LendingTree said in a report Wednesday. The network of mortgage lenders said the average 30-year, FRM at LendingTree branches fell to 4.71%, while the 15-year FRM hit 3.99% for the week ending June 7.  Rates on 5/1 adjustable-rate mortgages also fell to 3.27%. Analysts with LendingTree fear Dodd-Frank rules, including the qualified residential mortgage exemption that’s tied to risk retention, could depress housing prices and mortgage rates further. “Mortgage rates are continuing their nose dive, now hitting the lowest level we’ve seen in over six months,” said Cameron Findlay, chief economist of LendingTree.com. “While low mortgage rates are important for the housing market recovery, the ability of borrowers to qualify and take advantage of these rates is of equal importance. The federal definition of a Qualified Residential Mortgage  has the potential to severely limit the number of borrowers who can qualify for a mortgage, thus further depressing the housing market and pushing out the recovery timeline by years.” Week-over-week rates fell in every loan type, LendingTree said Wednesday. Freddie Mac will release its latest mortgage rates Thursday morning. Write to Kerri Panchuk.