EI and Ammonia/Ammonium Levels

I've been in the hobby for many years and have kept numerous tanks, but I started to get interested in maximizing plant growth and obtaining better algae control about a year ago. I assume many people followed a similar path as I did and started with Flourish and occasional root tabs before advancing to pressurized CO2. I used this for quite a while and there was clear improvement in plant growth, but algae problems continued. At this point I decided to start EI. I bought the EI package of ferts from Green Leaf Aquariums and began dosing it as prescribed. I dose this every other day and make a water change once a week. The water change is supposed to be 50%, but mine is probably closer to 40% when the refugium water volume is included. Algae control has improved, although I still find there is a red/brown algae that grows on the substrate and plumbing. I went ahead and checked water parameters today (I am supposed to dose the ferts today, so it has been about 40 hours since they were last dosed) and was a little surprised by what I found. My Nitrates and Nitrites were essentially 0, but the Ammonia/Ammonium was significantly higher than before I started EI. It used to be essentially 0, but measured about 4 ppm today. My phosphate level was about 5 ppm. I'm looking to improve my understanding on EI and ferts in general and have a few questions:

1. I am wondering why my Ammonia/Ammonium level has increased this much? Does this have anything to do with EI? The tank is definitely not overstocked and I have been feeding the same amount for 2 years.

2. It's also my understanding that if the pH of the aquarium is < 7, the Ammonia is actually ionized and becomes ammonium (NH4), which is not toxic to fish. Can anyone verify if this is correct?

3. I'm also curious why my Nitrate/Nitrite levels are close to 0. I assume the plants are taking up the Nitrate, but I'm still surprised it's this low with the consistent addition of ferts.

4. Based on this information, do I need to adjust my dosing regiments?

I'll give a breakdown of my aquarium below, but it is a well-established setup with healthy plants and fish. There are 6 adult discus in the tank and they show no sign of stress. Thanks!

60 gal discus tank (48Lx13Wx24H) with refugium.
Fluval 306 canister filter.
Pressurized CO2 setup. I have a drop checker in the tank and it is a bright green color.
Cryptocoryne, Vals, Swords, Java, etc.
Finnex Planted+ 24/7 LED that's on a timer. I have it set at "Daylight" and it runs for about 8 hours on the timer before being turned off. The refugium has a plant bulb in it and is on for about 12 hours. I used to run the refugium light 24 hours/day, but felt that it may be contributing to algae and cut it to 12 hours about a month ago.
I also have a Finnex MonsterRay color enhancing LED that I turn on occasionally, but it is not on daily.

 

Thanks for the quick reply! It just goes to show how doing something that seems so minor can lead one down the wrong path. You were absolutely correct. I thought I shook the bottles well enough before testing, but apparently did not (and feel quite foolish for having not repeated the process when the numbers were so astray). After vigorously shaking all of them, I rechecked and the numbers are completely different. About 30 ppm Nitrate, 0-ish ppm Nitrite, 0-ish ppm Ammonia, but 5-10 ppm Phosphate. I would assume based on this I can probably stop the KH2PO4 supplementation? Thanks again.