Okay...now I understand. I went back thru earlier posts to a month ago and this is the tree that had the mold at the base of the trunk.
Hmmmm...I'm really not sure what to do about the trunk base or, if that is related to the yellowing leaves. Hopefully our plant specialist (leatherback) can offer some advice about that.
In the meantime, I would follow his advice in his earlier post here and check for bugs (use a magnifying glass if you have one). Generally you will see most signs on the under side of the leaves but not always. Look for a mass of fine webs and a black peppery spotting on the leaves...this is spider mites. If you see tiny, oblong shapes the colour from light beige to brown to black attached tightly against the spines or veins on the underside of the leaves, this is scale.
I would also suggest going to the main menu of the site (upper left corner of this page), click on "Care" then go to "Pests and Diseases" read the info there. Have you researched this particular tree to find out it's specific needs? That too would be beneficial.
Leslie