My first thought was fabric softener as I have had similar spots from it.

I didn’t use fabric softener until the last washing.

Looks like grease spots. Try treating the spots with Dawn dishwashing liquid and re-wash in hot water.

I use Cheer for some of my dark colors but have noticed that it really isn't all that good of a detergent for cleaning/ stain removal and getting the stink out of clothing. I've had to use hot water and Borax to get the stink out.

I did some reading and saw that sometimes new washers expel grease leftover from the original build. I wonder if that’s the source? I will use some dawn next wash to see.

Did these stains appear after the first wash and are other loads affected also?

Be very careful adding Dawn into your washer. It will suds up like crazy and doesn't take much. ...usually if we pretreat with Dawn we than rinse it out in the sink.

Lantro gave good advice because if it is grease that should work...unless it already went thru the dryer. Just wet a spot with cool water, rub some Dawn in, let sit awhile, rinse out, than rewash.

It looks like an overload of dye to me...

As if when manufacturer dyed it the dye adhered more in different areas. However I think you would have noticed it when new..Unless you took them out of packaging and tossed in washer without taking a good look.

If it is grease, Dawn mixed with baking soda rubbed into the stain has worked for me. Let sit a bit, rinse and wash as usual.

There is a good chance they were there when I opened the package. I opened in the laundry room and tossed them in as I recall. But I will try the dawn option to see if that makes any difference. At least the marks look like the fabric enough that they aren’t terribly noticeable.

I tried to add a second pair but they are out of stock grrrr.