Mate, I feel for you. I have been there myself. Get a moisture probe, if you are overwatering this will cause root rot, which could explain. I know you said it dries out, but you don't just want it to feel dry. You want to check in 4/5 areas that there are no damp spots. If you let it dry properly, it will help. I have killed a plant coz of it being shit after over 50 days. Don't worry, you are learning.
I can tell you that all you need is organic light mix. 1 bottle of organic grow, 1 bottle of organic bloom + a moisture probe. Well cheap to get all that, even on the internet. At the start, do Not saturate the pot, lightly water it to make the plant work to find the water. Do Not feed it for the first 3 weeks.
Maybe this will help if you get an organics line, day 21... 2ml grow per litre, day 34, 2ml grow per litre + 2ml bloom, day 44, 2ml grow per litre + 3ml bloom per litre, Next feed 2ml grow per litre + 4ml grow per litre, continue that til the end. That is the highest feed. Feed it nutes every time after 3 weeks, don't water alone, waste of time in organics. No matter what pot size you use which does need to be at least the 5 litre pots, follow this and you will succeed. I plant the seeds straight in mud, water them lightly, then follow this feeding schedule. Which mud you use does make a massive difference. What ever country you are in, just order some bio bizz light mix + 1 bottle of bloom + 1 bottle of grow. You cannot fail with that! I did all the fucking around changing everything like you, now I just do that, also got over 10 oz from 6 fb#2 recently using these nutes + led