any increase in rent contributions for current tenants will be to a level that does not exceed 30 percent of the adjusted income of the tenant or the published existing fair market rent for comparable housing established under
section 1437f(c) of title 42, whichever is lower, except that the rent contributions of any tenants occupying the housing at the time of any increase may not be reduced by reason of this subparagraph (except with respect to tenants receiving section 8 [
42 U.S.C. 1437f] assistance in accordance with subparagraph (E)(ii) of this paragraph);