D'oh!!!

That would explain why I'm not seeing any color change yet - in fact, I've lost 9 fan leaves in total since the switch.
I think I may be setting a record for fewest fans possible without abject death being involved!

Guess I'll dose everything with more SuperThrive next watering and keep my fingers crossed.

Would more nutes help at this point, or is it a better idea to not feed until they've recovered and shown signs of improvement?