I need to do lollipopping if my plants have a total height about 40 cm?

I always lollipop, no matter how short or tall the plant is. Defoliation is good to do as soon as you notice that it's done stretching after you switched it to flower. this usually happens in week three, so i like to defoliate then. I remove all the leaves that cover any bud sites, which is easy to tell at this point, due to pre-flowers being present. If the leaf isn't covering a bud site, leave it alone. You also want to keep feeding it nitrogen through it's stretch phase. So, make sure you're still giving it veg nutrients for the first week or two, then switch to your flowering food regimen. If you're new here, please select the answer that helped you out the most by clicking on the "answer" button underneath what the person said. If you have any questions, feel free to message me on here. You can pull up your messages tab by clicking on the little airplane in a bubble. It's located on the bottom-right of your screen. I hope this helps!