Water

Hi
Is a good idea to use ph water ones a week when using nutrients I'm in coco soil

No. Don't give plain water in coco.

Is ph water 6.5 ok

If it has nutrients in it, but a little on the high end for feeding in coco. Don't give plain water, regardless of ph in coco.

100 percent coco should be ph 5.8-6.2. Can go down to 5.6 but I stay at 5.8-6.2. and no, do not water with plain water you have to use nutes. You're saying you're using coco soil though