Moody’s Investors Service has downgraded a combined $7.7 billion in residential mortgage-backed securities issued by Wachovia and IndyMac. The latest round of reductions, due to continued deterioration of underlying loans, involved $6 billion of RMBS from four tranches from four option-ARM-backed deals by Wells Fargo-owned Wachovia and $1.7 billion of IndyMac RMBS backed by Alt-A ARM loans.