Ps keep an eye on your PH check it daily if needed.

Yes depending on what stage of growth and how large your reservoir is. They may not move allot. With that low of ec I’m assuming your pretty early on. And it’s a slow gradual thing. Even with large roots and fully mature plants you may only see a slight shift in PPM. 50-100.

Another case of good gear ain’t cheap and cheap gear ain’t good. Use drops or get a ph20 or similar. If your in soil then maybe it’s not a big deal but in coco or hydro if any sort a few points can ruin your day. Also Vivosun is rebranded crap and their customer service is worse.

By the time I add in perlite etc I usually get 2/3 of a 5 gal bucket out of each of the four squares that comes in a 40L pack of canna. Each square also absorbs a lil less than a gallon. I generally will add at the very least some cal mag to that water I use to hydrate. My pots are 0.9gal and one square fills 3-4 of them.