Is this over proofed or under proofed?

My starter is very healthy and bubbles away reliably even though I have a very cold kitchen (60 F / 15 C).

Recipe: 100g whole wheat 400g bread flour 350g water 75g starter 2tbs salt

Mix and Rest 30 min (x3) Bulk ferment on counter for 6-8 hours then into fridge overnight Shape in morning Proof in proofing basket for 4-6 hours (roughly double) Bake at 400f for 45 min

What am I doing wrong? One sister says I’m over fermenting my other sister says I’m under fermenting.