Whole wheat sourdough starter not doubling after 4 days
I've followed Reinhart's instructions to create a soourdough starter using rye to start with followed by whole wheat (stoneground).
The batch rises from 14 fl oz to 25 fl oz, but never doubles. I have the feeling I could go on forever like this.
It is a hot summer here in the UK, around 85F. Could this be the reason?
Can I use the starter to make a barm, even though it is not doubling in size yet?
Thanks from a newbie