Right buddy I just wrote this for someone else so I'll share with you too. As your having ph issues I'll also point out that they can be caused by too strong a nute mix. As the plant absorbs nutes (or doesnt) the ph of the pot changes due to imbalances.
if your feeding correct doses, the ph of the pot will rise during veg then drop during bloom. To deal with this without all the fucking about you go in at 5.8 for veg and around 6.3 for bloom. That'll keep it ph perfect all the way as long as you've got the nute strength right.
As I mentioned, completely ignore what the manufacturer says. I don't need to look, I know it's a pile of nonesense lol. They all are. Here's how it works. .
some general rules for you.
Not an exact science but you can't go far wrong.
Feed wise, asuming they're growing properly they need 100ppm(NOT including the water) per week of veg.
4 week old plants needs 400ppm, 10 week old plant needs 1000ppm. Most strains take a little more during the stretch then level off once the buds start forming.
Once the buds are half formed you drop the Base nutes by half (roughly) and hit it with a PK booster.
Most strains can handle ppms a fair chunk higher than that but that's what they actually need.
Tops go yellow you up the micro nutes/calmag
Bottoms go yellow you up the Base nutes.
Brown rusty spots and you first make sure it's not caused from perspiration burn then up the calmag.
Leaves go dark or the tips claw down you lower the N which is in the Base nutes.
Tips burn is iether p or K I can't remember but if your not using a booster you'd lower the Base nutes. If you are using a booster then lower that.
As long as you keep the feed on the lighter side, up the doses a little at a time and stick to those rules then that's all you should ever need to know.
Again though, this is general guidelines you've still gotta judge it yourself.
For example, I've got 7 week veg photos that are still on 450ppm and apart from a little iron Def they're fine but it's because I had to keep them small for a while.
I've also had autos that needed 1000ppm by week 6 cos I made them go massive.
As long as you stick to the lighter side though the worst that can happen is some leaves go a little bit yellow. When they do you just up the feed and problem solved. If nothings going yellow then they don't need anything more.
Hope that's helpful for ya buddy.
Keep it green