Oh yeah, these have been on flush for over 3 weeks now. I started flushing at the end of the 6th week, based on assuming 8 weeks flowering time. Every time I'd change GH nute water, it was always distinctly darker in color, and just dirtier. The advanced nute water ends up looking clear, and clean. The charts show that you only need one week of flushing for adv, and I bet that's all you'd need. I'll still always give them at least two though. I'm about to unload my wally-world dehumidifier, cheers.