You can use distilled water bro, just be patient with your readings and measure them out over a period of time. It’s hard to get an EC value from distilled water because there is virtually nothing to conduct electrical current in there and since ppm is measured the same way as EC either one can lead you astray when using distilled. If you add nutrients and let them circulate for awhile so you can get a decent reading.
The last picture I seen of your plants they looked a little small to be running a ppm that high, at least if you did not gradually work your way up to it.
@Bogleg is gonna be gone like another 5 days or so I think.
If your super worried, do yourself another reservoir change and drop your nutes down, and don’t take PH or EC readings immediately. Wait 10-15 minutes then come back and check, make your adjustments, then come back and check again.
Hope this helps