WTF is this training? Oo
Lolippopping is only done after the stretch. If you remove mass during growth, not only do you reduce the surface area available for photosynthesis and therefore growth, but above all you stress the plant, which will have to recover before resuming growth.
You've already killed one plant, two are completely blocked and the last one is a traumatised monster.
I invite you to start again from the beginning, paying much more attention to environmental parameters such as the way you water your plants without giving the plant time to absorb everything, the amount of light, etc. and not doing any training whatsoever.
There's no shame in growing a Christmas tree when you're just starting out.