So I bought 2 kumquats from oscar tintori a few months ago, one with a short thick rootstock and one with a half-stock (alemow) rootstock.
At first they were fine but not long after (say about 2 wees later or so) the first one started dropping a leaf a day, sometimes 2 or 3.
When the second arrived, same thing happened.
Now after 3 months, the first one is almost bald, it has many new growth, new stem and leaf shoots (above the graft) but even the leaves and once a whole new tiny branch fell off.
In the beginning when they just lost a few leaves it seemed obvious it was due to the wind, our climate was also colder than it should be, so I moved them into the greenhouse.
Since they're nagami kumuats they should handle 38+ °C (this season it hasn't even gotten that hot yet inside there).
To aerate the greenhouse I do open the windows but when there's heavy wind they're only a bit open, when there's less wind but sun I open them medium and when there's a lot of sun but low/no wind I open them fully.
Weather surprised us sometimes so again I thought some of the new growth could have blown off from wind gusts, but it's getting calmer, less wind and I see the new kumquat dropping more leaves, even fruits and new growth too just like the first one. The first one who is almost bald seems to have stopped dropping stuff.
Since I do not see any visible pests right now and I did spray them a few times before when I saw pests on other citrus I exclude this from the list of possibilities.
There's no sign of leaf miner.
The first kumquat has perfectly dark green healthy leaves (which he dropped) and the second one has that too but a part of them are curled down (seems they grown this way because they're very hard) and have yellow edges, as if they watered it too much (it was like this on arrival) or nutrient deficiency.
I'm giving a fixed proper watering schedule and feeding them properly too (except that I gave them some CaMg a few times before I knew that was not good for citrus).
In any case the strange thing is that only those 2 kumquats are affected, other citrus nearby (shikuwasa, mediteranean sweet lime, kaffir lime) are unaffected. while they stand right next to them.
And yes, container size is too big, I know, but there is no sign of root rot. I feel deep in the ground before I water and it never felt moist when I had to nor did it smell like fungus.
The first kumquat (that is almost bald) did have pests in the beginning though because I found orange resin on a branch that was pruned by the seller, I was able to scrape it off because this stuff attracts ants. Afterwards I applied a mixture of neem oil with brown soap once a week for 2 times and I always did the other one too.