I did oxy, no help that I could see. I’m trying regular bleach now. next try will be bluing liquid. Then I’m done.

I have an Electrolux also. If you decide to try it, just use the bleach cup as a guide. I don’t know the measurement off hand, but it seems like it’s less than a 1/4 cup. Sometimes iron in the water causes discoloration. Maybe try the bluing first. Mix it up in a measuring cup before pouring it in. Borax is my go to for everything.

I don’t have any borax but will add it to my shopping list.

Chlorine bleach can cause yellowing of some fabrics ... mostly if it's not fully rinsed-out (keep rinsing until there's no chlorine odor) or if it chemically interacts with iron in the water supply. I've been using bleach for years on my whites -- socks, kitchen towels and dishcloths, bath towels and wash cloths -- nothing is yellowed.

1/4 cup would be the minimum I'd use in a frontloader to insure sufficient concentration. Maybe up to 1/2 cup maximum for a large/full load.

My Whirlpool Calypso HE toploader (the first HE toploader on the market 20 years ago) uses as little (or less!) water per-fill than a typical frontloader, and states to use a full measured cup of bleach for the Whites cycle ... but I don't think concentrated bleach products were yet on the market at that time.

Understand chlorine may lighten or make the yellow invisible but it won't actually remove the cause. I personally wouldn't use chlorine to whiten yellowed textiles without knowing the cause. It has the potential of making it worse

If you do use chlorine be sure to put it in the bleach dispenser so it's dispensed at the proper time and as said above continue rinsing until all chlorine scent is gone. I am rooting for you to solve this issue. You can do this unless it's a manufacturing defect.

So I used my Tyler High Maintenance wash with 1/4 cup bleach on the sanitize cycle with an extra rinse. I figured if I ruined them it wouldn’t be a big deal, they are ikea covers and were $40 each I think. Regardless, I think the yellowing is gone, although I’ve been staring at the duvet covers for so long my eyes may not be trustworthy anymore lol. I will take a pic later when the sun is fully up.

Well I’ve waited all day and it’s grey and rainy. So I took a pic in the dreary light.

This was the before pic,

I will wash again in a few weeks with sodium percarbonate in the sanitize cycle. I think they will be fine.