I love Silica... easily the most underrated element we use. I tell people to add a large res. when making the leap from DWC to RDWC. The greater volume will ease pH swings from Silica. They don't all do it, but Armor Si from Gen Hydro for instance will give you a pH of 11 and takes a while for it to chill out.
Silica Blast from
Botanicare is probably the tamest ive used. Im hopped up on designer Silicas now... there should be a 12 step program. My rig is 50 gallons total.
This may be a bit controversial... i get the fuzzy eyeball all the time for this... i use a very large air pump. One that goes way beyond O2 saturation. I believes it helps nutrients through the roots. It keeps the roots open and free from the side of the bucket where one can harbor issues. The only downside is some nutrients may foam up... Z7 is one,
Power Si is another, they will Lawrence Welk my room in a hurry, but i still use
Power Si.
Anyway... your plants look great. Get ready for the magic to happen.