You let her get to dry. Pick the pot up and feel how heavy it is. Dont let it get that light again.
You need to find a balance of letting her dry out a bit *needed for good root development* and not getting too dry. Too dry and she is always trying to recover instead of growing. Plants do have momentum.
Remember, even when you go with plain water you should be adjusting for PH. If you throw the PH off she cant eat the nutes that are in the coco right now.
Very rare was the day I used only water in coco, I just about always used some nutes and watered until I had enough runoff to make sure ph/TDS were in check.