Alex, when you said the leaves were yellow and veins dark green, the first thing that came to mind was a mineral deficiency, but after looking at your picture, I see nothing that indicates this problem.

What size pot was your citrus in, and what size did you plant to? If it's overpotted, that may be one reason foliage slowed-down in growth.
As for citrus soil, do you know what the mediums consist of? It may not contain any nutrients, therefore, citrus should be fertilized. They're semi-heavy feeders during growing seasons..They also require nutrients such as iron, magnesium, etc.
Also, because a soil is marked citrus, doesn't necessairly mean other mediums shouldn't be added..For instance, they sell cactus & succulent soils, but some are too heavy and will drown plants..they also sell house plant soil that's too heavy or too light..if too heavy, in either soils, Perlite and/or sand should be added.
I reread where you wrote the soil is a citrus/cactus mix..Never heard of this combo..I am curious what it consists of. Did you add any other mediums when you repotted?

Alex, there's definatly something wrong if your soil is still moist after 4-6 wks..Either you've overpotted, the soil's way too heavy, or both.
How many leaves have yellowed?
Alex, if it were my citrus, I'd work on soil and pot size. Otherwise, your kumquat will worsen and can die. Roots are staying wet which isn't good. Eventually, they won't be able to take in liquids...can't absorb oxygen.
Good luck, Alex..

Overwatering will cause leaves to yellow...the same w/underwatering, insects, lack of nitrogen, lack of minerals..Good luck, Alex..Toni

Hmm, I don't know specific size, but it's certainly bigger than the plastic pot that the tree came in, maybe one or two sizes bigger. Never really heard of overpotting and I didn't realize that was an issue.

I don't know what the medium contained, as it was a while back, but I do know it said on the package of soil that it was appropriate for citrus.

I'm guessing that the soil is probalby too heavy, or their just isn't enough drainage (the pot is one of those nice glazed clay pots, so maybe it's not as porous as it should be)

I didn't add any other mediums when I repotted. The plant doesn't get a ton of son each day, but it does get some, so i wasn't particularly surprised that the deeper parts of the soil were still wet after 6 weeks (mostly because when i do water, i soak it).

I do have some fertilizer, but now i'm worried to apply since it obviously it would require simply MORE water.

Thanks for the help,
Alex

Alex,

Perhaps you are overwatering, especially considering that the pot is glazed. In terms of watering, Four Winds provides the following guidelines in a "How to Grow" booklet that accompanies purchased citrus: "For the first watering, use a sufficient volume of water to fully saturate the potting mix and to see drainage from the bottom of the pot. After the initial watering, water as needed with enough water to fully saturate the top 2" of soil. The bottom half of the container will generally stay moist." And Four Winds recommends using a moisture meter to assess if watering is necessary or not.

Best of luck with your kumquat.

Jerry

Alex, do you know how a pot is measured? Using a measuring tape, place tape across pot horizontally. This will give the diameter..Check old and new pots.
1-2 sizes up is fine, unless roots are barely filling initial container.. If this is the case, there's no need to repot in a larger container..allow roots to grow in.

I agree w/Jerry about the first watering..You want to water thoroughly until water seeps out of drainage holes. While watering, cover all areas of soil, not one spot..
The only thing I disagee w/Jerry about is mid to bottom section of pot staying moist..Especially after 4-6 wks.
I agree using a water meter, but many ppl here on GW are against them..for one, it's said they're not accurate.
I bought meters from Rapitest.com They come in all sizes, shapes, test for pH, sun, etc. Guages start at 20.00 and up. Good luck w/your Kumquat..they're beautiful trees..Toni