Hello! I have a fruiting lemon tree in a pot I've been keeping since early spring this year. (attached a photo in the comments, as Im unsure how to do so in the post)
I've been noticing it slowly turn yellow green by the end-ish of summer, and it now has a bunch of leaves that are yellow.
Ive been looking online trying to find a solution, but the symptoms are a lot all over the place, so I'm having a really hard time identifying the problem.
-----------
Some of the older leaves were already yellow/deformed, but I've noticed them+others growing increasingly yellow, and have noticed some things:
1. It's mostly older leaves turning yellow (newer leaves seem to be more resilient) - some are turning yellow as a whole, while others are yellowing in splotches(some from edge, others from the inside out). Some leaves also seem to have yellowing veins, while other seem to rather have yellowing between the veins. Overall, the tree is very light green in color (even the newer, healthier leaves), so I suspect there is a general yellowing affecting all of them
2. There is wrinkling/outward curling on some leaves (especially the older ones)
3. Some of the yellowing, older leaves have black/brown spots, usually from the center of the leaf, starting from the veins, but other seem to have them from the edge. One of the leaves had it at its tip, which spread out and killed its edge. These brown spots seem to not really move to adjacent leaves, nor do they seem to be spreading across the infected(?) leaf. I have observed infected leaves very slowly growing in number(usually from older leaves), but they dont drastically increase in size after they have occurred
4. The leaves, especially younger ones, seem to be pointing upward (like, stiffly upward)
5. there are some leaves that show stunted growth. I got them around mid-summer, but got really nice large new leaves in another branch after that in the same season, so i dont know if this is a sign of something
6. I have 3 fruits on this tree. The fruits seem fine and clean, although seem to be developing slowly. Peculiarly, two of the fruits actually came out/grew out at the same pace, but I've recently noticed a big size difference between the two. (One is growing faster than the other)
7. The leaves have lost their gloss... They used to be very fresh-looking and glossy, but have recently turned papery. Some of them seem worse than others, and running my fingers across them does leave a residue on my fingers, but they seem more like dust than mildew
------
The soil is well-draining, and I fertilized with a slow dry fertilizer once around june, another around september. The fertilizer is 16-8-12 with micronutrients Mg2%, boron 0.06%. The package does say its meant to last at most 6months, not 3, but the old pellets looked very wrinkly/were mostly gone, and i was observing its fall in condition around early september, which was why i gave it then.
I do not see any mites nor bugs (have been checking very regularly), nor are there spotting on the leaves that seem to be indicative of them.
The roots ARE on the high-ish side (the dont peek out of the soil but seem to be present just centimeters off the top of the soil). I have covered with extra soil before, and they just keep climbing up. The roots seem to be in fine condition, and I don't smell anything off them (soil, leaves, roots all smell fine)
It IS fall here, which tends to be on the cold side, so I've slowly been acclimating it to the indoors (It's about 20~degrees celcius in the afternoon outside, and about the same in the evening indoors).
Ive thought about it being a lack of sunlight/cold temps, but I've seen its decline in condition(especially its yellow green leaves) since late summer (temps were about 25~30 degrees celcius at that time, with good direct sun). The days HAVE been getting shorter and colder though, which I suspect is playing a part in its condition.
I water/ed it with tap water with a tiny drop of vinegar throughout the summer when it got too dry, but stopped by the end-ish of summer as rainfall season came on (as the soil seemed to get enough rain.) The rain here in Seoul apparently has a pH of 4.9~5, so it might be on the slightly more acidic side.
I am worried about its condition, especially winter seems to be fast approaching... I've just purchased a grow light, and am planning to get some compost from my parents' house, hoping it will help.. I'm just worried it might be fungal, and that perhaps I should be spraying or providing it with something else.
Can anyone please help my lemon tree?