You said you repotted, then noticed the soil staying wet longer. Are you watering less often? Will you repot again with a good mix with lots of grit in there for faster drainage? Is your tree living outdoors where it belongs? Yellowing is most likely from sodden soil and rotting roots, but you need to not only repot using a peat-less and very gritty mix, but also put it outside, cut back any black or slimy roots to dry places, and use a one-time drench of the new soil with a house plant fungicide.