I'm taking a stab in the dark here, but did you drill drainage holes in your black planters? I bought the same ones a couple years back and they didn't have holes until I gave them some.
The largest size they have... idk... 4-5 gallon. They're awesome, for a plastic planter. I particularly like the rim... I snip paperclips to size and bend them to fit, generally in the shape of a hook and slip them over the rim to LST and otherwise guide the plants, using string.
I gave most of them away, as I switched up my method of growing. But I kept one... the only grow I've got going this year is in that large planter. It's just a last ditch effort to get some bud in my jar, nothing particularly special. Maybe I'll upload some pics.
I'm heavily considering doing something similar to what you have going, hydro in a tote, numerous plants, and probably SOG/Scrog or the like. I'm no hydro grower though... I have a small (immature/stunted) plant that I started as a hydro experiment - it's not doing well, but there's hope that I'll be able to bring it through once the roots are established in the water... the roots haven't dropped from the jiffy cube yet so it's a micromanaged grow. Oy lol
