Smelly Drainwater, how smelly does it get ?

It's not normal to smell piss without organic nutrients especially if the water input doesn't smell like piss. Could mean that you have some roots rot , the smell makes me think that your roots rot is more than a few days old. Someone mentioned hydroguard which is a good option. I would have had enzymes with the next feeding to break down the rotten roots or some hydrogen peroxide ( I'm not 100% sure about the last one so google search it to confirm ). If it's a roots rot you'll need to find why your roots are not doing good. You mentioned an homemade hydrobucket with coco medium in it and even if it's hard to believe : plants in coco medium an be overwatered which could lead to issues on the roots so maybe you should reduce tbd watering frequency and settle a dry/wet cycle