PSA: spent 3 weeks blaming spider mites for my jade plant's leaf drop, it was my tap water
My jade plant started dropping leaves in November and I went full detective mode, checking for webbing every morning with a flashlight and even bought a $14 bottle of neem oil. After about 3 weeks of treatment nothing changed, so I finally tested my tap water with a cheap TDS meter and it was reading almost 400 ppm, way harder than the rain water I used to collect. Turns out all those minerals build up in the soil and the plant just slowly chokes, which is why the new growth kept going yellow even though I thought I was doing everything right. Switched to distilled for 2 waterings and it already stopped dropping. Has anyone else in a hard water area run into this with their succulents?
Honestly jades are tough as nails and I've watered mine with straight tap for like 8 years, ppm probably close to yours, and it's fine. Leaf drop in November is way more likely just the plant going dormant plus less light, that's totally normal for jades that time of year. The distilled water fix might just be a coincidence with the season changing back, but hey if it's working for you then keep doing it, your mileage may vary.