The first plant has brown pistils, the 2d &3rd white pistils and reasonable volume, the 4th is at least 2W behind!
Do I have to cut all at the same time?
Sharing same DWC, diseases risks to harvest progressively and let roots only?
Na I’ve cut plants like this earlier than other ones sharing a reservoir/tote. You’ll be fine.. roberts suggestion for something to keep it sterile is sound advice.