it look like overwatering I know that sounds stupid since its hydro but what is your media and how much air are you running in the system DWC need tons of air, when I did DWC I use BC Neuts because their mix gives you 2.0 EC with out testing and it works great, I now use top feed hydro system.
I use Great White Myco in 4 hydro set up with zero problem and kick ass results https://www.rollitup.org/members/terek2k-169968/albums/nirvana-blue-mystic-12412/
I have used it for the last 2 years with great results I add the dose of 4 mil per gallon at the start of the 12/12 cycle, recently I started using it in veg and the results are great the internodes are stacked tight and my plants are still large it dhould increase my yeild and bud size by 25%
I goto my local plumbing store and buy 1/2" bulkhead fitting and connect a barb fitting to it for my hose.
The bulk head attaches by drilling a hole in the bucket and it has gaskets that seal it.
I can post pics if you need