Troubleshooting a starter

Greetings,

I have had a starter going for a few weeks now, and what I am noticing is that it isn't doubling and the bubbles are small. I have good activity, after eight or so hours the top is very bubbly, and it will pass the float test, but I am not getting the bigger bubbles and doubling that I expect as signs of a healthy starter. I am generally sitting at about 75-80 F, and have my starter in a cabinet above the stove. I have been using 1:1 flour water by weight (grams) and the flour I am mixing about 70/30 all purpose/whole wheat. I am not sure if I just need to give it more time to mature or what. 

A week or so ago, I tried to make a loaf (75%) hydration, gluten development looked good with the stretch and fold method, but the bulk ferment (totaling 6ish hours) did not see much rise in volume, which indicates a week starter?

I started a starter from scratch a few years ago, and had a much better doubling/bubble size than what I am seeing. I am just not sure what I am missing in this context. 

I have been using Stone Ground Rouge De Bordeaux Whole Wheat flour from Barton Springs Mill in Tx and King Arthur unbleached all purpose in my mix. I began with just the whole wheat flour and water, and later switched to a mix. I have attached two photos of my starter below.

Thanks for the help!