Off putting odor on day after nutrient change

Root rot or some bad bacteria probably. Maybe algae if your bucket doesn't block the light completely. Make sure you have a good bacteria like hydroguard provides. This will stop bad bacteria from getting established. This is especially important if your res is warm. I keep my air pump right next to the vent on the bottom of my tent. Cooler air is being pulled in from it so the pumps sends cooler air to my reservoirs.

Also just to add if your Ec is as high as your diary says then your going burn shit out the plants. Knock that down to ec 0.8 for the seedlings.

Hello. Please cut down on the amount of sugar you use at this early stage. Use some, but you are using way to much. The bacteria that eats it are causing the smell. Chuck.

Hi there. Temperature is really important when doing dwc if your at a constant high temperature your roots will start to smell. Also some nutrients do leave a smell that's not nice, I usually bin them after one grow if I don't like the smell. If your roots are brown and slimy then the smell could be root rot. I wouldn't run a res for more then 10 days. With frozen bottles helps but you don't want them touching your roots.

DWC is very particular. From what I know, yes the temperature of your solution is extremely important and you must keep it chill and cold, but for the question about the smelly bubbler I don’t know enough about this type a culture.