The red leaves on the one Red Sunset is not due to chlorosis. Chlorosis does not present as red leaves but rather leaves that have a washed out, pale green, chartreuse or yellow coloring with darker veins. And that could be due to either an iron or a manganese deficiency, both of which are common with alkaline soils. With red maples the deficiency is typically manganese.

There is no easy fix for this. Acer rubrum just does not tolerate alkaline conditions well and it is just not a good choice of tree for those conditions. You can do some temporary fixes addressing the Mn need but you are unlikely to get soil pH anywhere close to what it needs to be.

As to the red coloring of the new leaves, I'm not sure what to attribute that to. Are you sure it is not just the flowers you are seeing? They appear before the tree leafs out and are red in color. It's definitely NOT chlorosis but possibly some other nutrient deficiency, the source of which may also be the high soil pH.

The leaves are definitely Red, it's not the flowers. I found the information about the red leaves on maple trees on the site that seems to point to this as the issue - https://www.the-journal.com/articles/when-your-maple-turns-red-before-its-time/

LOL!! That "source" is just a newspaper and they have no idea what they are talking about. Do some research on iron or manganese chlorosis, what it looks like and how it affects red maples grown in high pH soils.

As I stated, the early red leaves may well be some other nutrient disorder due to alkalinity but it is just not what's referred to as 'chlorosis'. The word itself means 'pale', 'pallid', 'pale green' or 'greenish yellow' and is derived from the Greek word khloros.

Thanks. I posted here to get some ideas on what to try to correct this regardless of whether it is the iron chlorosis or not. I've already looked online and not found any other information explaining what it could be (other than the link I shared), hence why I posted my question here.

It sounds to me as if you are disturbed by the new red growth which may be entirely normal for newly emerging leaves.

A photo would really help- it really could well be you are concerned over nothing. That the leaves are emerging differently colored than your other Red Sunsets could be simple mis-labeling.

I certainly would not do any knee-jerk soil amending until I knew for sure.

What pH gauge are you using? Any chance of you getting a real soil test done to verify?

If you are in the USA you need to be in contact with your local cooperative extension agent for a soil test every few years anyway- you can also send them photos and ask questions via email.

They are a great resource as far as your LOCAL conditions and things going around.

Please see attached photos. Again the other two sunset maples I planted at the same time in another spot have green leaves. I will look into a soil test if there is nothing urgent I should be doing to the soil...

Those leaves don't look like Red Sunset. The relatively deep sinuses would seem to indicate that it's more likely one of the freemanii's.