Mystery weird marks on DC PE t-shirt. Detergent stains?

[ChocoMarmalade]

Can anyone please help me figure out what these weird marks are on my DC's sports t-shirts? I tried to photograph the stains. The t-shirts are made from polyester and I am washing them at 30degrees for 59minutes using Unilever's OMO 3-in-1 laundry capsules. The t-shirts smell fine after washing but they look grubby because of the marks.

My kids are 5 and 7 so they don't sweat a lot so I don't think it's oil/sweat residue.

Could it be laundry detergent residue? Is there a way to get rid of the marks so I don't have to buy new t-shirts. I have Vanish and white vinegar in the house but I don't know what the stains are as I don't get them when I wash my Zumba t-shirts which are made from a similar fabric.

Please help solve my laundry mystery!

I'm watching as my son's PE t shirt has the same marks and I'd love to know how to get rid of them!

From my experience they look like classic greasy fingerprint marks that won't come out at 30C, the water's not warm enough. You need at least 40C and some decent soapy detergent to get them out.

The fabric conditioner could be causing this. Best to avoid fabric conditioner with sports clothes. Try rewashing shirt in sink with an ordinary detergent ( or washing up liquid). Less likely is that the drum in your machine isn't turning properly so the detergent /fabric conditioner are not being agitated enough to dissolve and disperse properly.

I agree they look like greasy fingerprints but it's so weird because they still have to wash their hands a lot at school post-pandemic and there isn't any greasy food on offer in the school canteen, not even chips.

I will try pre-soaking in Vanish and then putting on a 40 degree wash to see if that works. I will report back!

@ItsDinah, that's an interesting suggestion about the fabric conditioner - I will experiment with an ordinary detergent.

I generally bung everything in one load without separating anything, but think I will have to do the sports clothes separately if the fabric conditioner is the culprit.

It looks like spots of mould. Where are they stored?

Have your kids been playing with bubbles? I found that some types of bubble mix were leaving dark stains on DDs clothes.

Fabric softener can make the pipe that drains the machine greasy. If this goes back in the machine slightly it can cause greasy marks that don’t come off. We have had it before and it didn’t affect everything in the machine just random items. We actually stopped using softener and it hasn’t happened since.

Just a quick update - I think the stains were caused by the fabric conditioner but nothing has shifted them. I tried soaking them in white vinegar and then washing at 50degrees with plain detergent and an extra rinse cycle, but the annoying marks remain. Lesson learnt and I will buy new t-shirts.