URGEnt - leaves turning yellow

.7 EC for that plant should not be an issue. My concern is it looks like you have nutrient lockout due to pH imbalance. You should be targeting a pH in soil of roughly 6.2-6.5 for every feed and water. Our plants have a particular pH range where they can uptake nutrient. There is a helpful sheet someone did that shows all the nutrients and their pH absorption range. When the pH goes out of range they cannot up taken up by the plant. I suggest that if you do not already have a pH reader that you get one asap. Then you can flush out every pot you have with a pH adjusted water to correct the pH of the soil. When doing this I like to use roughly 3-4 gallons of water in a 5 gallon pot. Most of the time I take the plant to a mop sink for easy cleanup I hope this helps.