Poolish and Cold-ferment

[Jersey Pie Boy]

So, I baked off my five day-cold-fermented poolish dough last night...and the results, consistent with my last attempt, remained disappointing. Still tasty, and no complaints from DW but I remained frustrated by lack of  fully developed flavor and less-than-stellar oven spring.

Adapted from Ken Forkish, with small hydration change ( though I should probably use it as he suggested..will detail below.

Poolish 



125 gms AP flour  100% 
125 ml water at 80 degrees F  100%
1/32t yeast    .03 %  based on entire recipe

Poolish made night before..covered till active and bubbly..was about 12-14 hour at 68-ish room temp

Final dough

All of Poolish
125 gms bread flour  100 %
1 tsp/ 5 gms salt  2%
50 ml water at 105 degrees F   40%   (or would this count as 70% based on total?)  Forkish suggested   50 % or  62ml (not counting the water in poolish)..This would give, he notes, a        total dough hydration of 75 percent..pretty tricky to work with).



rested 10 minutes, then 3 stretch/folds. Bulk fermented 8 hours at 67 degrees, then ball and refrigerate for 5 days


Last time I made this recipe, I noted that it would excellent at 3 days..flavor and OS, but by 5 days, not as good. Seems to have happened again, though this time, I had no 3 day marker to test against.

Where am I wrong? In my expectations, or my execution?

Thanks!