Yellow leafs

Looks hungry. When feeding autos remember less is more, and when watering them. there is no magic number, its based on how much is the plant drinking and how much are you providing. its a dynamic value and should be reevaluated every time when its getting bigger and stretching. This gets tricky when you have feeds that are to high or low in concentration but the plant still wants more water as the overall volume being provided is low. You can avoid overwatered symptoms by mixing in more perlite into the medium and keeping them roots oxygenated, this way even if you provide to much water it will drain and not supersaturate the medium. Overwatered = Limp Leaves and Stiff Stems Underwatered = Extra Limp Leaves and Limp Stems As for EC strength. 1.4 is high for autos IMO. They can go into early flower from feeds that are too strong, something that looks to have happened already. https://www.thcfarmer.com/threads/med-man-method-ppm-ec-chart.73326/ this link its a nice reference point. take from it what you will. Notice they use a 700ppm scale for 1.0ec where as most western places use a 500scale, someplace use a 640scale. PPM's are a calculation based on EC, 1.0EC is 1.0EC no matter where you go. Best to always use EC vs PPM. Good Luck!