I see zero indication of a pest problem in your tree and suggest that you hold off on using the neem when it's not warranted.

Do you have any idea what what the pH of your soil is? That it is clayey can be a challenge for this plant, but I think that you know that.

Coloring of the foliage is normal, but if you feel that something is seriously wrong with this plant, we need better images of the whole plant.

I didn't know what a 'Japanese Blueberry Tree' was so I looked it up. It seems reddish coloration is normal for this genus just before seasonal leaf fall. (Evergreens do lose their old leaves, just not all at once like deciduous trees.) Like rhizo, I see no evidence of pests. Elaeocarpus.

A brown or bronze tinting of the youngest leaves however will not be seasonal leaf fall. Was this discoloration - which appears to shown by all the leaves in your pictures - present before you sprayed the oil?

My link says the old leaves colour spring before they fall. I'm not referring to the colour of a new flush. Pictures at my link show red on old foliage. The same is true in the OPs photos.

Jonathan has their hand beneath outer foliage in their pictures, clearly indicating thereby it is the brownish tinge that is the topic of concern.

I'm not seeing anything more than a bit of bronzing consistent with older leaves at the end of winter and a few red leaves in the background.

Bought it from a tree nursery about a month ago, our home/lotwas a new build, so ground hasn‘t had this bermuda grass or the top soil when I planted it.

Bronzing was occurring prior toe spraying the oil.

yeah, I need to get my emotions in check because this my first tree and the most money I have ever spent on something I planted.

please see the attached pics, let me know if you need a particular angle, is from 2 different sides.