Inverse osmosis system was installed

Calmag it to about 150ppm, let stand for 10 mins and then add nutes on top, then pH. You dont wanna use npk to raise your ppms / ec, but use a correct strength npk nute ppm once your water is at a good baseline.

The more important question is do you have the correct nutrients for RO water? Even base nutrient for soft water don't normally contain enough background EC to sustain perfect health and you might need to bring the EC up to around 0.2 with a bit of calmag before you add your base nutrients. To answer your question though, you'll need to add more food to make the TDS 1.4EC

So your water had 0.4 EC out of the tap? Wonder what it was... First you have to add back in your Silicon and potentially cal-mag so that will shift up to some value. I would leave it there and watch my leaves rather than risk adding too much which could be a catastrophe. You can always up em, hard to get that stuff out of there once they eat it.