How can adding organic fertilizers to feed water Lower the TDS reading?

I brew aerobic teas to fertilize my outdoor grow. When using rain water 50% mixed with aged tap water with a HIGH TDS of over 500 to get a water at about 250ppm I then add mycorrhizae powder, powdered bat guano, worm castings, kelp and fish extracts and black strap molasses in amounts about 1/4 recommended and wind up with a LOWER TDS than before!! How can this be? I have read that organic nutrients don't have the same EC as thier salt based versions. Maybe they even lower the EC? I assume that my TDS meter is using EC and converting it for my "convenience" but is that the reason why the weird readings? I don't see any sign of nutrient burn. In fact since starting the "mini" tea brew for month old plants when they are only drinking a few cups a day, my grow looks better than ever! Deep green, three feet high and already with a "trunk" as thick as a pencil. (Girl Scout Cookies and Gorilla Bomb)