Yes air to the roots is very important. I am currently using
thesethese air stones. I have at least 1 per bucket 2 where I can. For my next run I am looking at
thesethese circular ones. The finer bubbles give more surface area on the roots so happier roots.
You also need a strong air pump to push enough air. The water in my DWC buckets looks like they are violently boiling. I currently have
thisthis air pump. It is a little loud but if you put a tube on the input end it is pretty quiet. That style pump is cheaper but louder and lower quality. If you spend more you can get a very strong air pump that is also quiet.
I have not used OG BIOWAR but I use Mycogrow which is made to fight root diseases. It is kind of expensive to run all the time but if you are having root problems it might be worth it. You might also want to try Southern AG Organic Fungicide. Again I have not used this but I plan to because according to the ingredients it is a more concentrated version of
Hydroguard.
I checked out your link for your grow. Are your plants in the shallow bin still?