Pic would be nice but wth I'll shoot from the hip.
Not enough light or light to far away.
Boiling tap water is prob killing most everything in there so Calmag is prob needed.
Wtf is the vinegar for?
From everything I have heard MG is not the type of nute you want to be using. Get some true nutes.
What's temp like??
What is PH like?? In Hydro if your PH drifts to much you will NOT be succesfull
How old is plant??
I think you should get the idea that you need to provide more so things can be diagnosed.