Possible nitrogen/magnesium deficiency

Ph and ec not important in soil grows outdoors where rain keeps ph in check and salts from building. It is important indoors to keep an eye on things, if you want the best grow you can do. Cheers friend

you can grow many soil harvests before thinking of ph ec if ever... and im not sure of testing runoff unless you want to flush and who even cares then a few buckets should do well. Maybe above makes a little sense if you use coco or of course hydro.

you have not updared diary. depending on soil it sounds late to start with nutes so lets see what happens from here.

Make sure your not keeping it wet all the time, let dry between waterings. You should keep your ph and ec in line with a ph and tds reader. Make sure proper ph and ec is going in and make sure your runoff water is within those values as well. Cheers friend