The hard water is locking out your cal and mag plant intake. Renyman and the others are right. Get distilled water flush to balance your plant.
Unless your familiar with the nutes that your using, everything else is simply guess work, since your at the mercy of the mix instructions of your nutrient info that your using. Your approach is right to start small with the nutrients, but your plant is choking from the water ph and chloramine. Flush... Flush... Flush... and Flush to get the salt out.
At the very least, use vinegar to lower ph and balance accordingly or baking soda (to increase ph). You likely won't be able to rid of the spots, since it is already damaged. Affected folliage should regain its green luster, once you flushed your plants, and continue in your veg cycle with the right regime, you will begin to notice increased growth in the leaves, color and overall plant response (leaves lifting and dropping).
Is this a different plant from the other plants in the past? Some plants are more sensitive than others, and plant varieties have different tolerances. Nevertheless, it will stunt (stress) the growth of your plant and overall lushness, since it is not getting a well balanced set of nutrients.
Note your leaves are already beginning to loose luster and have a faded green...
1. FLUSH
2. BEGIN nute feeding again with ph balanced water.
3. Give it some sunlight.