My white t-shirts are going grey - how to keep them white?

This thread was marked as solved. Here's a summary of the problem and the fix, generated from the discussion below.

White T-shirts gradually turning dull grey/yellow despite separate washing

The problem

The user’s white T-shirts were gradually becoming a light dull yellowy grey even though they were washed only with other white items. The washing machine was described as an old Bush model that otherwise seemed to wash normally. The user was using Ecoleaf liquid non-biological detergent, no fabric softener, and air drying.

Likely cause

The accepted reply said environmental detergents often do not clean whites as effectively as standard detergents, so the detergent choice was considered a likely contributor. The reply also noted that fabric softener can leave perfume residue, but the user had already said they did not use softener.

What fixed it

The accepted recommendation was to try a detergent that keeps whites properly white, as the current environmental detergent may be underperforming. If a more effective detergent has an unwanted perfume smell, the suggested workaround was to run an extra rinse-only cycle after washing to help remove the smell. No confirmed repair or machine fault was identified.

Checks to try

• Washed white T-shirts only with other white items
• No fabric softener used
• Air dried washing
• Previously tried Dr Beckmann Glowhite without obvious improvement
• Chlorine bleach did not seem to help

Parts or tools mentioned

• Ecoleaf liquid non-biological detergent
• Dr Beckmann Glowhite
• chlorine bleach