Looks like nute burn to me BUT What kind of tap water and what is it's PPM before you add anything ?
Chlorine, chloramine burn from tap water Looks like lock out or nute burn. Flush with R/O or distilled water for a few days and stay away from tap water unless it's from a well and you know what's in it. It's better to start with nothing in the water and add only what you want.
Your ec would only be 1.2 to 1.6 and depending on the meter to covert to ppm's would be 800.