Use of amphetamines in general can cause vitamin and mineral deficiency's. However, its very unlikely to be so severe that you develops scurvy. Vitamin c is in everything now a days, hence the reason why scurvy is rarely seen. Much more often amphetamines lead to vitamin d deficiencies, which many people have before amp's are introduced to the picture.
Meth mouth is caused by numerous factors. Severe dehydration, malnourishment, sleep deprivation ect....