How to make them top stronger

Hi you have a fair nice bit of space there air and water play a big factor in thickness of the stems well I can appreciate you have fans they aren't doing alot on the floor to be honest you need to hang them I see you have a fan higher up but it's far away get more air to the top on the stems and they will thicken up.

Здарова друг! Чтобы ветви окрепли поставь хороший обувь самого растения чтобы качалось на ветру и лампу чуть ниже

I never have that problem when I use silicate. You can still try to add it now and get some results. Cheers

U can tie the branches to the top site of your grow room.and then branches can rely on that.

Sounds to me like you're not giving her enough water when you DO give water... make sure you're getting a 10-20% runoff each time... the plant needs to draw water upwards and if there's not enough given to her, she's not going to be able to get any to the top to nourish it... Good luck.