Low sodium and exercising

6 months ago, I started a vegetarian diet. I have also adopted a no added salt policy in my diet. A month ago I started exercising regularly for 30 minutes of heavy elliptical workouts twice a day. Lots of sweating. Lots of water, but no salt or energy drinks. 

I started charting my food intake 5 days ago using Cronometer. I noticed that my sodium is low. The past 5 days are 1000, 1100, 800, 2000, and 400.

My potassium also seems to be low most days as well. 3500, 2700, 2400, 3300, 2600. 

How accurate are these results, and should they be of concern?