A good mix that many use 
Typically you’re looking at 4-6 weeks on fresh soil before nutrients is needed.
When you transplanted that new fresh soil added will add to that time if not start the 4-6 weeks over.
I grow mostly in coco-coir and perlite so I feed nutrients every watering with my coco plants, but when I do grow in soil, I often don’t have to add any nutrients till well into flowering if there was a transplant, if not a transplant then typically just before or right at flowering with most autoflowers.
Lots of variables that can change this but that’s “the norm”.
Checking runoff numbers is a good way to know, as stated above 1000ppm is usely the target.
I watch for my runoff ppm to drop below 800ppm or so then I feed to get it up around 1000ppm.
For example if runoff is coming out around 500ppm then I would feed 500ppm or a little over. If coming out at 600ppm then I’d feed 400ppm or a little over if that makes sense.
Crank that baby up at this point, the middle one and the one to the left is in flower and the other one probably will be transitioning soon.
They can handle 100% of the light’s power and you think they grew fast so far 
Turn it up to 100% and watch them explode 
Amazing looking plant’s for a first grow and compared to the average, you’re doing alot better then “pretty well”
You will make it to harvest I’ve no doubt…
Coco-coir and perlite mixed useing GH Flora series “aka trio” or GH maxi-series which is a one part powered or Jack’s 321.
All those nutrient lines are tried and true.
General Hydroponics trio or maxi-series (Maxi-gro and Maxi-bloom) is what I’ve used exclusively for many years now.
I’ve never had a ph issue that was caused by the nutrients used, PH issues in the latter part of a grow is most always due to bad watering habits, as microbes live and die as oart if the natural cycle, it’s important to get a decent bit if runoff so the ph doesn’t drop from the biological breakdown of organic matter.
If you search under my profile, everything I’ve ever grown was useing GH trio or GH maxi-series no matter the media used.
Heres a very useful video.
