I kept reading where people added rye or wheat flour to help "feed nutrients" to the sourdough starter. so... I went and bought King Arthur whole wheat flour and instead of 100g of white ap flour, I used 40g wheat and 60g white along with my 100g of water. The starter did rise but it didn't bubble throughout the mixture like normal and it didn't rise as much. I thought maybe it didn't like the wheat flour? so I emptied all but 100g of starter and added 100g white ap flour with 100g water. its still not rising like it should. what happened?!?! For the past two weeks prior to this, every time I added my ap flour and water to feed it, it would rise GREAT. Is my yeast that finicky?!
Don't know the "why".. but I ran an experiment a month ago and posted about it.. I found that AP bread flour is like crack for my starter.. great full rises.. but using bread or whole wheat and it gets lazy.. no idea why.. didn't get an answer.. and have moved on realizing that sometimes it's okay to just do and not worry about the why.. it works for me..
I use only WW flour for my starter, usually store bought WWW, and while it doesn't rise as high as AP or BF, it works fine in bread.