I look to spread mulches in autumn, replicating nature’s leaf fall, so yes pull back the poly in Oct/Nov and spread whatever compost you are using, perhaps water too unless the poly is letting rain through.
Then keep the ground covered, with poly over the compost until spring, so that weeds trying to grow are gradually dying in darkness. Check in March-April to see if there are still new white & yellow shoots of weed stems, if none you can remove poly and start planting, or roll it back a strip at a time as plants come ready.
