PH problems (DWC)

Not sure about buffering your solution, but please remove the bottle, your seedling does not require hyper humidity, cannabis is not a rain forest pant! It needs good air exchange to function properly and air movement to strengthen the stem. By having it inside a "sweat lodge", you increase the risk of fungus one hundred fold and it can also cause excessive stretching, not to mention the risk of actually cooking your plant. Cannabis has survived for tens of thousands of years without any special treatment, it will be just fine in the open air.

Vinegar evaporates, and is not a suitable ph down. Phosphorus ph down will work a lot better.

Apprntly you can also try lemon juice to change the Ph, never tried it but its the organic way and been told it works. Cant hurt right? as far as aeration goes- heres the science. if you test the Ph of very fizzy soda- its will be super acidic. if you let it go flat it becomes less acidic- why? Carbon Dioxide will cause a chemical reaction making the soda more acidic, so when it goes flat, it becomes less acidic. There are lots of diff gasses in the air ur using to aerate the water with, including carbon dioxide. This is why. It shouldnt change much thou, but it will get less acidic without aeration.