comments:
Take this with a grain of salt because I use fabric pot but I have to water my plant about the same size as yours, 3.5cups of water every 3 days now and it's growing healthily. To me it sounds like you're underwatering if anything, I wouldn't let the pot get "dry" half way down I'm pretty sure you want at least some kind of moisture in the root zone(i water if it feels pretty dry down to my second knuckle and pots light). But don't take my word for it this is just from my personal experience I'm pretty sure you just have a nutrient toxicity if anything don't add nitrogen to the soil for now.. and if you can I would water like like at least 6.5PH or up water because nitrogen is absorbed better on the lower end of the PH scale (5.8). I use a budget friendly $10 Vivosun meter, and it’s actually worked great for me. Just a heads up, though.. it won't give an accurate reading in pure zero nutrient water (like distilled or reverse osmosis water). These meters calculate PPM by measuring the electrical conductivity between their prongs, so they need minerals in the water to get a reading. That isn't an issue for my setup, because my tap water naturally contains enough calcium and magnesium for the meter to function, and my plants handle those minerals just fine. https://www.amazon.com/Hydroponics-Accuracy-Measurement-Household-Drinking/dp/B08HLXBBK4/ref=sr_1_4?sr=8-4 My tap water comes out at 6.8PH but after letting it gas out the chlorine in it for 24 hours, I find it at 8.0PH which is dangerously high to be giving my plant. And in turn when I added nutrients it brought it down to 6.5 which was exactly what I wanted anyways. That was nice but most the time I have to add PH down, if you skip this stuff you're just gonna have problems. On top of that your soil Ph can be off, put 1:1 parts of distilled 7.0ph water and your soil into a cup, mix, and ph test if it reads 5.5 or something you know your soil ph is pulling the waters ph down with it and is probably like 4.0(dangerously acidic) in which case you actually would want to course correct and water with slightly higher PH water than you normally would although I'm pretty sure your plant would be instantly cooked in 4.0PH soil xd.. just something to think about