Yellow sulphur is available at most garden centres.
With the shorter daylight hours and decreased light indoors you will find you will get more of the mould growth with growing indoors, i have this problem as i grow some of mine indoor at present. Do you have anywhere you can put them outdoors say in an unheated porch as the darlingtonia definitely needs a dormancy period and the draught from being outside should help keep the mould at bay.