OK Friend, so I've been TRYING to stay out of these threads but you are SO CLOSE to perfection that I have to say something.
I've been growing high times award winning material for 30 years now and one can take that or leave it, but it's a fact.
Do NOT waste you money on further tools like a ph tester or further accouterments like this supplement or that supplement. You are already RIGHT THERE.
Your ONLY issue is that you're keeping them in beer cups PERIOD.
Please ignore everything else.
I have used every mix I could make or find on the market and I'm back to straight Fox farms out of the bag.
This is an overview of my regular garden.
This is Chem 4 tested at 22%
My award winning "Duh"
And my namesake "Demosthenes Rainbow / Urkle"
So here's the deal friend.
Ignore everything else, you do NOT need ph meters and supplements and anything else except a final size pot.
I would advise 5 gallon (you can do 3 plants with one $13 bag of Fox Farms) or as in my case I use 7 gallon and collect 6 ounces per plant.
Plant from beer cups to final pot and veg them out.
Keep it simple friend, you are trying to do way too much.
You are on the right track as far as watering them, I only water when the container is light, doesn't matter if it's 3 days or 3 weeks, I water by need not by schedule.
Do yourself a HUGE favor and stop trying so hard. Just up plant them, IGNORE PH, IGNORE EC and PPM meters, it's ALL a scam.
NEVER add ph up or ph down unless you know you have a problem out the gate, otherwise the plant requires the drift through the ph table in order to uptake different nutes at different phases.
If you adjust to a specific window, then you will only uptake whatever uptakes in that window.
Repot your babies in 5 gallons and then do not water for 3 weeks. they will not start to wilt until runners have been sent to the edge of the pot and all available water has been consumed in pot.
Then when you water the plant will double it's size in 5 days. I GUARANTEE.
As far as nutrients go, yes I'm sure you are experiencing salt buildup in the beer cup. Think about it.
Otherwise...we can get into line ups if you want but I'm really done preaching to people who really don't want to hear it so if you respond in a positive fashion I will move forward with you, if not then best of luck growing.
Demosthenes
PS here are babies in beer cups and then again 2 weeks later in veg.
Final product 60 days later. No PH meter, no E meter. Just the basics.
Best of luck grower.
.