That happens when I add nutes too and I also use baking soda. My numbers going in are usually 1200ppm or so. Sometimes I go up to 2000 if the plant is not showing any problems.
Watch the runoff numbers for diagnosis.
Plain water going in should give a runoff of over 1000. Under that needs feeding. If it is much over 2000-2500 runoff, you probably need a flush to remove built up salt.
When feeding, the runoff should not be much more than what goes in.