Actually these are more black spots than brown. I did a quick search and it seems like more than a few have described this condition in dwarf Singapores- and others have said black spot or rust. Can anyone tell for sure and what I need to do about it?

Anything on the underside of the leaves?

Nothing underneath, except the black spot seems to go through, or at least be seen through, the leaves.

I believe it is fungal related but not significantly detrimental at this point in the growing season. Even though S.O. is at least semi evergreen the leaves will start to yellow and fall off in the next couple of months anyways. I am pretty sure I have some with same or similar spots.

In the spring consider using an anti fungus spray starting fairly early in the growth season and continuing on recommended intervals through the summer. Your last picture in the above sequence shows a leaf stem or something on the right side tip. Is there or was there some other damage in this area?

Those marks there look worse than they are. Seemed to be some creases from when they were shipped and haven't gotten any worse. Thanks for your kind help. Someone else told me to cut off all the sick leaves, and let it go dormant. Think I may do that. I isolated it from my other plumeria as soon as I saw it and keeping fingers crossed others don't get it.

Thanks so much, and if you have other ideas would love to hear.

Nancy

Let it go dormant on its own schedule. I like to let the leaves fall off by themselves as the plant draws back into the stem the energy/nutrients from the leaves. Not everyone has this option but IMO its the best approach.