Reddit reviews Micro Essential Labs pHydrion Urine and Saliva ph test paper , 15 ft roll with dispenser and chart, ph range 5.5-8.0

It's not fungus gnats.

You have multiple deficiencies going on at once which means the first thing you need to do is check your pH run off, not the pH of the water/fertilizer solution added to the soil. Make sure it is around a pH of 6.5 or so. Some fertilizers can acidify the soil forcing the pH down. You also have some slight tip burn which means adding more fertilizers would likely be detrimental.

5.5-8.0 pH strips are an easy way to read pH run off as they require no calibration, no special storage techniques, only need a drop of solution to work with and are accurate enough.

https://www.amazon.com/Micro-Essential-pHydrion-dispenser-5-5-8-0/dp/B0001SR4NM

You must have the pH in the proper range to really do a proper deficiency evaluation.

But it looks like a nitrogen deficiency (lower yellowing leaves) and a potassium deficiency (spotted necrosis caused by proteins unable to form/repair themselves). Proteins degradation is just a part of plant life and allows plants to re-utilize amino acids but potassium is vital to protein synthesis. edit- this is caused by "nutrient lockout" from an improper pH

Calcium deficiencies tend to have leaf edge burn due to an osmosis imbalance that destroys cell walls. In this case the higher salt concentration in the center of the leaf is pulling nutes from the leaf edge destroying cell walls. This is why some crops like lettuce are often calcium boosted to protect cell walls since leaf edge burn in a leafy crop like lettuce greatly devalues the price of lettuce. In lettuce and other leafy crops this can be caused by to much light in a day. You don't appear to have this issue.

There are nute deficiency charts out there which are giving suspect information which is why you may have come to the calcium conclusion.

So get the pH in control before adding more fertilizers or you can make the problem worse by further driving down the pH.

Potassium hydroxide ("pH up") is a fast way to raise the soil's pH (don't use sodium hydroxide!) and most any of the (bi)carbonates can act as a pH soil buffer since the carbonates will stay in the soil longer (don't use sodium bicarbonate or baking soda). Sodium can interfere with potassium uptake.

I'd go to an aquarium store, but I bet amazon has what you need. From a quick search:
https://www.amazon.com/Micro-Essential-pHydrion-dispenser-5-5-8-0/dp/B0001SR4NM/ref=sr_1_17?s=industrial&ie=UTF8&qid=1549996021&sr=1-17&keywords=pH+strips

https://www.amazon.com/CellarScience-AD640LB-Potassium-Carbonate-lb/dp/B074D9BXRT/ref=sr_1_3?ie=UTF8&qid=1549996084&sr=8-3&keywords=potassium+carbonate

I've tried using cheap pH meters in the past (fish tanks) and they always fail, give me bad readings and cause a panic. If you don't want to invest in a good one, I would suggest strips. Something like http://www.amazon.com/Essential-pHydrion-Saliva-dispenser-5-5-8-0/dp/B0001SR4NM/ref=sr_1_14?ie=UTF8&qid=1451476877&sr=8-14&keywords=ph+strips

I'm working on my 4 x 4 build and the research I've done says 4 plants in 5 gallon smart pots is just right.

I've heard that certain types of water don't quench thirst like other water. I can't remember what the deal was, it's been a few years, but it had something to do with the type of water you're drinking. Some water doesn't really satiate the thirst and stick around and go where the hydration needs to be in the body like other water. I can't remember the name, but there was some device that does something to the water to make it better for you and more hydrating.

Found this news story from ABC at the link below, and it has to do with the alkalinity of the water you are drinking. Distilled water, for instance, is very bad for you, because all the good stuff has been taken out of it. It can actually cause bone loss, which it did to me for many years before I got a clue that I shouldn't be drinking it. You can also get alkaline test strip paper and use your saliva to tell how alkaline your system/body is. Foods like sugar can cause your body to become more acidic and some fruits and things like pineapple can cause the body to become more alkaline. Having an acidic system can cause your body to be more likely to lean toward health issues, while having an alkaline body is better for your health.

There are at home machines that can make alkaline water for you, and there is also alkaline water you can buy. You can also add drops to your water to make it more alkaline. It's good to use the test strips to test the bottled water you are drinking, because there are many bottled waters on the market, even name brand bottled waters that are actually less alkaline than is recommended for human consumption. Possibly you are drinking one of these waters and it is leaving you dry.

https://abcnews.go.com/Health/alkaline-water-claims-offer-greater-hydration-health-benefits/story?id=33268980

Here is the test paper like I have at home. I've had it for a very long time and it still works fine. You can use it to test the saliva or urine that comes from your body to see where your system stands. Just tear off a small strip, test it, and compare it to the colors on the cartridge to see where your pH level is at, and respond accordingly with whatever changes are needed to make your body more alkaline and more healthy.

https://www.amazon.com/Micro-Essential-pHydrion-dispenser-5-5-8-0/dp/B0001SR4NM

And here is an article on the importance of having an alkaline system...

https://www.livestrong.com/article/444199-what-are-the-benefits-of-alkaline-in-the-body/

I would buy ph up and ph down as well as some hydrion test strips (the ones that run from like 5.5 to 8 not the larger range). Use them to adjust the water after nutes are added, or if not adding nutes just adjust the water by itself (adding nutes to water affects ph so you want to adjust after, not before, adding them).

Your target range for soil should be 6.6.

6.4 or 6.8 is acceptable as well but no higher or lower if possible.

Meter I use: [here]https://www.amazon.com/gp/aw/d/B01A0MHHBW/ref=mp_s_a_1_8?ie=UTF8&qid=1505272717&sr=8-8&pi=AC_SX236_SY340_QL65&keywords=ppm+meter&dpPl=1&dpID=31jdwwwK2WL&ref=plSrch

pH strips I use here