I fucked up.
Started seeing deficiences: magnesium, calcium, potassium, sulfur. The leaf twisting was a dead giveaway.
The algae in my reservoirs hadn't given me any issues, even though this is the third run. But I think some fungus grew to eat the dead algae - and brought down the pH level of the water. So I cleaned the reservoirs.
Part of me wants to supply microbes via compost or a tea, but I worry those acids will not help the pH if that's truly my issue. Taking pictures to compare day-to-day. Crossing my fingers.
If they do not improve, I will try a flush. Soil still smells forest-y, so hopefully it will recover.
Still in veg, but these buggers are big now.