A little help or advice on ppm's in aerogarden

2 PLANTS ,2 1/2 FT TALL , 400W HPS , PH @ 5.9 , SUFFICENT VENTILATION , ROOM TEMP @ 75 DEG. ,, JUST WENT TO 12/12 4 DAYS AGO, SWITCHED BUD NUTRIENTS, . HAD ABOUT 15 LEAVES FALL OFF TODAY, CHECKED PPM'S AND THEY WERE @ 1920ppm, any suggestions !! thanks

I do 200PPM for starting into veg after the seeds/clones establish. When signs of being hungry start, I bump to 400PPM, then to 700PPM, then 900+ PPM depending on what the plants tell me. I go by how the plants look and not by a time schedule.
I move up slowly as being hungry is easier to fix than nute burn.
I think your way high and the plants are burning. Flush with zero nutes for a few days then start low and work up from there.
There isn't really a one schedule fits all.
Since the aerogarden is hydro, I would PH 5.5-5.8 to avoid nute lock out.

thanks or the advice,, truely appreciate it !!

Dhead: One of the things I've liked about growing with my A/G's is that I haven't had to worry about PPM's. I use Technaflora's "Recipe for Success," mix it by the gallon, keep the pH at 5.8 and change it weekly. I use it from the seedling stage to harvest and I've had no problems. My friends with bubble tubs seem to be involved with a much more sophisticated method of growing and they've got more meters and testers than an auto shop.