What is wrong with this plant?

First I would like to address the pesticide and fungicide, for organic pesticide (especially against aphids) I would base it on tomato leaf extract water since it has naturally strong resistance to pests (if you grow tomatoes in your garden you'd notice they're the only ones not getting eaten). For a good organic fungicide a combination of neem oil, dish soap, and baking soda would do great (plenty of recipes online that you can base it from). Now for the overwatering, Overwatering can be avoided completely by applying good drainage (from both substrate and pot) and your choice of a fabric pot (not sure if that's what you're using but seems like it from the few photos you have) is very good but the media mix you chose has poor drainage. The vermiculite is what holds nutrients, holds moisture, provides aeration and drainage especially when growing with soilless media (coco-coir), in your mix the vermiculite should have been at least 33% (1/3) of the media but what's done is done, for now I would suggest just spacing out your irrigation more and as indication water when the top 5cm of the media is completely dry just to give your roots the oxygen and room they need to grow (this also prevents root rot in the future). Lastly the nutrients, unfortunately I don't know much about organic fertilizing but I am able to recognize late stage potassium (K) deficiency on the second photo (green veins, yellow foliage, and chlorosis at the tips) which is probably caused by the low pH in your irrigation solution, since you are growing in soilless media I would suggest trying to raise the pH to around 5.5-6 with a slow increase with 6.5 as the limit. the first picture with the dark green foliage, light yellowing, and tip chlorosis is probably the same problem in an earlier stage plus a little Nitrogen (N) toxicity (from the three macro-nutrients nitrogen deals best with acidity) so you might want to consider lowering the nitrogen fertilization by half and slowly working your way back up. To conclude this long ass answer (which I hope helps) this is my subjective opinion to what your grow is experiencing and it is based on my experience. Overall your grow looks good and would probably do amazing if you manage to mend whatever your plants are going through, remember cannabis is a very resilient plant that can withstand a lot of stress!! **And my personal advice is always go easy with nutrients, deficiencies are easier to spot since they appear faster and cause less stress to the plant than toxicities!! Hope your grow goes well and the harvest bountiful :)