Teeth can't come in decayed. They need to have been exposed to sugar, and for bacteria to have eaten away through the sugar and into the tooth. It sounds to me like a vitamin deficiency (or possibly too much of a vitamin).
Consider these milk teeth to be the canary in the coal mine. Start a food journal, noting everything she eats (and I mean everything). Then check it with a nutritionist, or just do some research online on amounts of vitamins and minerals babies of her age need, and what foods supply those amounts.
Ruth Yaron's Super Baby Food has charts that make this easy. She covers all of this in great detail, so all your bases are covered. Probably, if this is a vitamin or mineral issue, you will figure out what it is, and start increasing the foods that she needs to overcome the deficiency (or balancing out what might be causing an oversupply) and she'll be fine. But you really want to intervene ASAP so she doesn't suffer in other ways than just her milk teeth.
One way to start to get a handle on this immediately, before your detective work gets you answers, is to offer your daughter a great variety of very healthy foods. Wean out anything that doesn't deliver a serious nutritional punch. Even snack foods (which, for toddlers, make up most of their diets) must be healthy, nutrient-dense foods, not what fall under our adult conception of treats (cookies, unhealthy crackers, processed foods...). This is for the very reason that snacks make up most of a toddler's diet. But it's all the same to an 11-month old, who doesn't have to know that canned, drained, rinsed, mashed (i.e., choke-proof) kidney beans aren't popular, tasty snacks (try 'em. They're pretty good!). Cook her up some red lentils (takes 10-15 minutes), don't salt them, maybe add some Italian herbs, and mash them up to use as a dip for foods that she doesn't like as much on their own. And let her choose her snacks from a variety, which you offer. Studies show that, when offered a variety, even very young children will choose the options that give them what they need at the time. Kind of like a pregnant woman who has a craving. It's the body telling you what it needs.