What happened to my plants?

BTW looking back I now know the problem was chronic underwatering, I would water too often and get fungus gnats, so watered less often but only 0.5-1L per time instead of 2-4L for this pot size... Also too many nutrients for this plant size 1-1.5 biotabs would have been enough.

Sieht mir nach einer überdüngung aus. Schau mal ob der EC - und PH Wert des drains passt. Es könnte nämlich genauso gut sein, dass der PH Wert nicht mehr stimmt und dir Nährstoffversorgung dadurch gestört ist. LG.

Nitrogen deficiency starts bottom up. When yellowing occurs top down, it is a deficiency of micro nutrients/trace elements usually. Those tabs are not ideal, they require that the substrate is always moist to work properly, and cannabis does not like constant moisture. I also think that nutrient distribution is too localized and not as evenly distributed as when using liquid feeds. There are plenty of good quality bio/organic liquid ferts on the market that work perfectly with living soil.

Nitrogen deficiency mate. Adjust your feed and check your PH is correct. Good luck bro