Constant EC during Flower NFT

You should give what your environment and your plants allow. It's not a one-sized-fits-all answer. Even if somone uses the exact same products and substrate, they may still need a slightly different EC than you. A higher or lower VPD compared to someone else will impact the "optimal" EC of your fertilization. It's not a single point. It is relative to several factors. If the plant is healthy long-term - meaning all the way until senescence is impossible to avoid - then your EC is fine. If you get deficiencies or toxities you adjust the formula accordingly. If 1.8 works flawlessly, then you don't need to change anything. If you have to constantly "flush" or similar behaviour, it means you are overfeeding. Observe the plant and adjust accordingly. There are too many moving parts to think that a breeder's or fertilizer maker's instructions are absolute. These are merely starting points from which you need to optimize for your local variables. The plant decides for you. How is it growing? What's happening over the course of several months? Shitty formulas can work fine in the short-term but will eventually cause issues. Any fertilization methods that requires regular "flushing" is a poor method of fertilization. Keep it simple. Don't overcomplicate it. Read and react... what evolves is what is right for you.