Something wrong?

I am gonna go with a potential salt build up from feeding without proper drainage to rinse out old fertilizers.

Over fed. In soil it should be a schedule of plain water/plain water/feed/plain water/plain water/feed....... Make sure that when you do irrigate, that you get a good "run off", that is, water coming out of the bottom of the pot. This helps to prevent nutrient salts from building up and causing problems. Also, instead of giving 8 different fertilizers each time you feed, give 2-3 base "grow" nutrients and 2-3 supplements one week, then the next week, the same base "grow" nutrients and the other 2-3 supplements, so that you rotate through your fertilizers. This is more effective than trying to give a little bit of everything each time. 18/6 is also the best routine, you won't get any real extra growth by using 20/4.......... cannabis plants NEED adequate "sleep".

It's just a shot in the dark. Droopy leaves is usually a sign of overwatering OR under watering. Your diary says you water 0.5l per 5l pot per day, ir sounds right. Considering the size of the plant, root system should have already filled more than a half of the pot. Judging by the pictures you don't water all the surface of the pot, probably roots can't expand due to dry soil on the sides. Some older leaves look like having Nitrogen toxicity (tips bend down).