need more info ,,,,,,all plants dont feed the same , some are light feeders some are heavy feeders , you start out light , read the plant and work your way up weekly , what nutes are you using , what plants are you growing ? if it were mine id be at 1300
If it were mine I'd be between 900-1100 (at.7) but as mentioned, alot depends on the strain.
What are they at now? Flood and drain are pretty easy, you just watch the ppm of the main res. If you see the ppms going UP after a few days, then its a little too high. If they are going DOWN every few days, then they are a little too low. Also, never move more then 100 up or down at a time.
Thanks for the advise starting a flood drain table with different strains. Now i know i have to calibrate an average to feed all the plants with no burns. Will try stick around 900-1000 PPM.