Sensi Skunk

In soil you will get the best range of nutrient absorbtion around a pH of 6.5 It can vary a few points up or down without any issues though. As far as your ppm it doesn't change with pH. I assume this is an issue with your ppm meter. And as far as the best ppm. That is really impossible to answer. There are a lot of factors in the environment that affect what ppm your plants will need. Your ppm of your water is pretty high though, so I would try to get a ro filter or really and kind or water filter will help. And if you are using a good quality soil then you shouldn't need to feed for about 3 weeks or so. Just keep an eye on the leaves for anything unusual and try to keep the environment right. Looks like you are off to a good start. Good luck with your grow!