You may have more luck posting this is the laundry forum (there are some real laundry gurus there).

I would want more information about these sweaters. What material are they? Cashmere? Silk? Are the embellished with something?

I personally love Vaska Herbatergent (I have the lavender one) for my fine washables but I also have the Laundress Wool/Cashmere. I'm not a huge fan of the Laundress line but the wool/cashmere really does do a beautiful job. http://store.thelaundress.com/merchant.mvc?Screen=CTGY&Store_Code=TL&Category_Code=135woolCash

Here is a link that might be useful: Vaska

Buy some shampoo at the dollar store, see if that works. You night also try using "Dryel" dry-cleaner substitute that works in the dryer. Other than that, it may be hopeless. My experience is, once a delicate material is ruined, it can't be revived.

Detergent is a consideration (I use the same product they use at a museum here in NYC to care for their fabrics) but it might help to consider how the item is washed, dried and blocked. I tend to focus more on the material type than any one brand for all clothing, so my contribution would be to also consider the process if it's worth it.

There are a bunch of folks here who've tried a TON of detergent brands. You'll find one! :)