First of all, what are you feeding with ?
If it's organic stuff it shouldn't be too much of a problem in terms of salt-buildups. But things still can accumulate.
I was thinking 1,65 is mighty high, but then again you're at the end of flower, so they eat lots.
Depending on the strain and how long it usually takes to mature, I'd start giving them tap water only anyways now...say it's an 8 week strain... I'd just give them plain water now... that will certainly help to get that EC down and you'll see they'll start to fade nicely soon...
Some folks say it's unnecessary to "flush" in organic soil, or even counterproductive, but remember this is not a flush, you're just stopping to feed them so they use up what's left in the soil and after that what's stored in the leaves...
I use well water at 150ppm no teas or bottled nutes - the ppm of the runoff by the end of the grow is in the 1500-2000 range afaik. I don't typically use meters growing without nutes. I'm not sure ec tells you much if you are not using chelated salts