I have been trying to make sourdough starter for over a month...and having problems...it really will not “double”, altho the whole wheat one seems to be getting there (I resorted to making 2 different batches)
Try leaving your jar with just pantyhose and a rubber band around the neck to keep out bugs. Also try rye flour. Rye superboosts the wee beasties. Rye make super active starter that triples or more. Can not explain why but it does.