Starter not doubling but looks active on day 4/5

Toast

Hi everyone,

I'm on my second attempt for a starter. The first one I lost track of a bit and it got funky so dumped it. Both times I've followed the King Arthur recipe here - so wholewheat flour to start and discard/feed with all purpose:

 https://www.kingarthurflour.com/recipes/sourdough-starter-recipe

At this point day 4-5 it's not doubling, perhaps 1/3rd increase in size by the time the 12 hour feed point comes up - bubbles on surface, usually 10-15 what I think of as small-medium sized, no huge ones. For each 12hr feed I'm measuring out around 115g starter and adding 1/2 cup water and 1 cup all purpose flour (store brand). Water is mains - it's hard but doesn't taste/smell chlorine at all. Resting pace is on top of wine fridge - pretty consistent 70-73F, and typically 73F through the day.

Wondering if:

  1. I should just continue as is, and hope that a couple more days gets more activity
  2. Find a warmer spot (perhaps microwave with door ajar/light on - or oven with light on
  3. Adjust feed ratios
  4. Or - amazingly - is it maybe even ready?

I doubt #4 - but would appreciate any direction possible re #1-3!

Thank you,

JW