No not at all. Obviously RO water makes a difference but with tap water, if comes out of the tap at 300 ppm, just add that to your desired ppm. If the water is 300 ppm and you want your nutrients to be at 700ppm, then your nutrients should be at 1000ppm . So fill the res tap water at 300ppm and add your nutes until it hits 1000ppm. If were talking about the last 2 weeks, then absolutely. It is totally fine to give them tap water for last few days. Quick question, if plants must be flushed with 0ppm for 2 weeks to be considered "good", what about all the outdoor? You know, since there will always be organics, bacteria, microbes, metals, minerals in soil, in the earth, it cant be "flushed" fully so.....? (Its not about feeding 0ppm for 2 weeks, its all about not giving the plant more than it can eat)
So many nutrients are immobile, like calcium becomes a part of the cell walls, no amount of flushing will ever get that out. Its all about EXCESS. The problem is feeding the plant more than it needs and a build up occurs and the people that claim flushing works is because theb2 weeks of plain water allows the plant to eat all the extra food youve been giving it that it has stored in the leaves. To anyone that wants to debate this, i ask that you jut try it my way once. Feed less through flower only feed them what they need and then gradually taper down for the last 2 weeks. Plain water for last 3 days just in case there is any food left behind. If you do that, dry and cure properly and still have an issue, i dont know what to say. Sorry about that guys, i just see this debated all the time here and it gets tiring. The problem with this industry is that so much of our information came from word-of-mouth, 2nd hand info, bro-science, and grower stories. Not a lot of science made public until recently because most of this industry operated clandestinely and couldnt exactly verify our findings in a lab. Now that we can i think its important to move past old ideas and remove stigmas about the whole subject in general. Ok sorry you guys had to put up with that but i had to say it