3 weeks old, when to start nutes, run off ppm 957

This is my 3rd grow. I need some opinions on when to start nutes. Just want to make sure this one is good from start to finish. It's an AK48 fem. I've only fed distilled water to date. It's in BioBizz light mix substrate. It's actually growing great and I have about 7 good tops already. I transplanted after two weeks and topped 3 days later. I finally got a TDS meter and I tested the runoff after feed today. It was 957 which I thought was pretty high. The plants don't seem to mind. I'm planning on LST'ing her in another week. Then give her another week (maybe 2) of veg then flip to 12/12. When should I start grow nutes before flipping, if at all at this point?

Anyone?

don't bother with grow nutes. they don't need much unless its been in a pot forever or if its a giant. neither seam to be the case. plus seams like your soil is hot enough.

you can start adding cal-mag or something like it closer to the switch date. avoid purple stems.

I've never used BioBizz but it looks like a diluted potting soil, to get better drainage, and give the ability to feed sooner. First testing the run-off from soil will contain and lot more dissolved solids than those contributed by a NPK level.
Next I wouldn't think that the food in this mix would last more than a few wks, I'd start feeding soon at a low level, and increase slowly. Slow and steady wins the race.