Why does it mean that? Did you read that somewhere? It is false.
My tap isn't far from that. you are fine. It's not the cause of any problems.
Also, EC conversion to ppm is garbage. Find a local water quality report... do you have a well or 'city' water? That will make a big difference in some areas. If i had a well, i'd be up around 1000 ppm given my area's water table. i've used soft water the last 3-4 years and saw zero differences in my fertilzation needs. I am soilless, so i provide 100% of nutrition through irrigation and nothing else, so it's easy to make these claims with confidence. My formula has not shifted nor did it have to shift changing from hard (300ppm according to local water quality report before it is softened) to soft water. The Na it adds is miniscule. In a soilless context, it's irrelevant with runoff and in a soil context it's irrelevant to anything potted plant less than 1-2 years old - i.e. at some point it could build up in a potted plant, but not in the normal context of growing weed... a mother plant has a concern when using soft water long-term.
Add fertilizer based on need.. ignore the starting EC. If you have gauranteed analysis labels, that will tell you far more accurately how much of each element you are adding than an EC (TDS) probe that can use 1 of sever conversion factors for EC-to-ppm... that alone should tell you the total lack of accuacy in that conversion. The factor used is not based on anything other than brand name. It's whimsical and only mildly correlated. Brand of tDS probe will make a 40% different ppm while testing the same volume of water.
the EC reading is accurate, to be clear... and super high EC can cause problems, but you'd have to get up around 3.0 and higher. you should not be adding 2.2+EC worth of fertilizer in any common sense context. You are hydro, so 500-750ppm of well-balanced nutrition is all you need depending on life stage and how you fed prior. Your tap is a bit hard, but not in a dangerous realm if it's ~400ppm. Generally, you should be fine at 500ppm and less... general guideline, not a rule written in stone.
A cheap hose filter might reduce it by 25%. You'd need something expensive, like RO, to significantly reduce PPM. The 25% might be enough and may not be necessary to start.
I'd suggest something similar to the following for mature vege plants:
PPM
120-130 N
40-60 P
180-200 K
100+ Ca
75-80 Mg
100ish S
As you near flower, you may need to drop N -- when foliage starts to get dark/lush, drop down to 80-100ppm N. This can very as to exactly when it is necessary. A lot of it depends on how you feed early on... fertilization is a culmination of everything you've done from seed to present. How you fed early impacts what is needed later. You can see this is only ~650ppm.
As vege growth stops, you'll want to dial back again, slightly... trial and error will find that happy zone. By this point the plant should be nice and stocked up in the leaves and fertilization should just be maintaining health or maybe a very slow degredation of canopy is okay too - as long as it can finish strong and healthy. A little fade is not necessary, but ensures you are not overfeeding.
If you provide extra co2 and/or tightly control temp and RH you may need slightly more. Max potential photosynthesis per day is something that varies based on conditions. Better conditions will use more nutrients per day. it's a balance of several factors playing out over time. either way, this is a good ballpark to start in, then observe and adjust as needed -- that last part is always necessary. There is no 1-size-fits-all formula, but minimal adjustments will be necessary from this particular formula.