when do you feed flower nutes?

so im about 2 weeks in a photo run, and i see on the tops it starting to bush out with white hairs, my question is when would you start flower nutes?

I start flower nutes after 1 week of 12/12. But only go 1/2 strength the first week. Then maybe 3/4 after 3-4 weeks.

I start at the first sign of pistills, 1/4th strengh then up it every week

I start when I flip my lights to 12/12....

3 answeres that are very diferent haha guess its another one of these debateable topics? im at day 15, with signs of bud starting too develope on the very tops. so next water i will add some food at a 1/4 str. do you guys use ro water or tap that has been sitting out a few days?