The essential part of alpaca health is keeping them at the correct weight. Too heavy and they may have trouble getting pregnant, their fleece “blows out” or becomes course and are naturally unhealthy. Too skinny and they cannot keep a good body temperature, are may not produce enough milk for their nursing cria and may be suffering from worms. Ironically, they often have silky soft fleece because their body is trying to stay warm without the help of natural body fat.
In winter alpacas can lose condition, because of malnutrition, and this can be masked by the fiber covering on the animal. Just because they look fluffy, the body itself may be super skinny and unhealthy.
There are many causes of malnutrition in camelids. But in each case the way to affect a remedy is to notice it early, and react to the signs. Alpacas can drop weigh quickly but it takes time to put it back on.
The best way to check is to get your hands on the animal and "body score" it.