Need Help with My Hindi Kush Autoflowering Babies in Hydro

please can anyone help me..i have two autos growing that are seven weeks and one day old.. this is when i first planted them in rockwool. i'm not sure when to start to flush them out as i've read they are ready to harvest at nine weeks but all of the hairs are still clear and i don't want to start to flush them till the right time..could anyone tell me of any tell tale signs with a plant that can let me know when to start the flush. i'm very worried aboutthis as i've had alot of trouble with these plant but with loads of love and care they pulled through, i went to amsterdam for four days, came back and all my plants had stem root, lost six plant but these two babies are little warriors so Need help please..i know they are going to be sweet smoke any help would be brilliant cheers.. i know this is the place to go for info.. big fan of the site

there are no signs of when to flush. if you are feeding with synthetic nutrients you might want to give it a full week before harvest with water only. if you have organic nutrients in your soil or feed with organics, I just use water for the last few days and never have had an issue.

youre best bet you be to figure out when thell be ready to harvest and flush a week before