Ds's tooth became grey just before it developed a cavity and broke. It wasn't fast, over months. But, I didn't think much of the grey, until the tooth started looking brown and then it cracked off.
There are a lot of gut healing alternatives that help with nutrient absorption and support the immune system. Basically, when the ph of the gut is out of balance, the ph in the other orifices is out of balance and the "bad" bacteria grow and cause cavities, yeast, thrush, etc. Enamel on the baby teeth is related to nutrient availability (calcium, magnesium and phosphorus), and nutrient absorption in the gut also.
Several easy things to do are coconut oil, cod liver oil, bone broths, magnesium, zinc, vit C, probiotics, especially whole food probiotics. There is a thread "Healing the Gut" with more ideas:
http://www.mothering.com/discussions...d.php?t=434071
Sorry you all are going through so much.
Pat