Can you dim the LEDs instead of shutting them down completely? Or at least reduce the photoperiod?
It might help to know the exact setup of your DT light. How many of each type of lamp, and what you're driving them at, what photoperiod you run, both for LEDs and other lights (on the DT only). That would provide us another piece to the puzzle. But I'm thinking it's a combination of lighting and skimming. I agree that the growth on your scrubber look great, comparable to some of my best growth weeks.