The leaves of my plant turn yellow and brown spots appear, and eventually they turn brown and dry. This phenomenon sometimes stops and sometimes continues

Root issues, Likely getting a bit of rot and lacking in oxygen. Control your watering habits more and I'd also say amend more perlite into the mix next time but it looks like it has a lot. It can also do this from root damage like an aggressive topdressing or pest, but I do not think this is pest related. I also do not think this is N related. Good Luck!

Poor drainage/being waterlogged/too wet all the time.

It appears like your plant is taking Nitrogen from old leaves and moving it to new growth in the plant. Nitrogen is a mobile nutrient meaning it can be taken out of old plant tissue and moved to places where the plant thinks it needs it the most to survive. They are very smart when it comes to this. Give the plant some more Nitrogen in the next few feeding but be careful not to over do it because you are in flower and the Nitrogen uptake is much lower during flower. I hope this helps.

You have Nitrogen (N) deficiency

Raise EC and Raise humidity around 55% focus more on P.K