maybe the tap water you're using has too much chlorine. anytime you use tap water, it should be left in an open container for 24 hours before watering with it. this will evaporate out chlorine and other shit that humans are adaptable to, but plants aren't as much. it will also allow the water to be room temp when you water, so you don't shock the roots with cold water. this is just a guess that it relates to your current problem, since it really does look like a nutrient deficiency