how to clean yellowing woollen baby clothes?

[pinkr]

Hi, I have just gotten my old christening blanket and done old knitted cardigans down from my df lift...there are one poor two yellow spots on them...looks almost like rust stain but can't be...can anyone recommend the best way to try to clean them. They were knitted by my gran and are almost like lace. Thanks

Isn't vinegar good for this kind of stain? I'd check it out but I've a feeling it's an old remedy.

Thanks I'll try that!