Looking at census, on-line trees, bmd's etc. it would seem to me that there were in fact 2 James Nash's married to a Christian.
The one who married Christian Stowe was bc.1771 and the online trees show she died Aug.1833. The children baptised at Potterne 1801-1807 definitely their's. However, this James Nash was an Ag. Lab. In 1841/1851 he is living with his eldest son Isaac and a widower which would concur with the death of his wife Christian in 1833. This James Nash died 1852.
1841 - Devizes, Wiltshire - ref. HO107 - 1184 - 2 - 5 - 2
James Nash 60 J. Carpenter b. Wiltshire
Christian Nash 50 ditto
Sophia Nash 30 Not born Wiltshire
Christian Nash death recorded as Christianna Nash Sept.qtr.1845 Devizes.
1851 - Potterne, Wiltshire - ref.HO107 - 1839 - 388 - 6
James Nash 74 Wid. Retired Carpenter b. Stert, Wiltshire
Sophia Ellen Nash 41 Unm. b. Bath, Somerset
Martha Ember 9 granddaughter b. Devizes, Wiltshire
(not sure where Martha comes into things - can't see a marriage of a female Nash to a Mr. Ember).
James still alive in 1861 and died 1864.
The online trees have lumped all the children born to a James and Christian Nash from 1801 to 1823 to James Nash and Christian Stowe (including Vashti) - I personally don't believe any of those baptised at Etchilhampton belong to this couple.
One James bc.1771 Worton, Wilts., Ag. Lab. married to Christian Stowe - she died 1833 and he died 1852.
The other James Nash bc.1777 Stert, Wiltshire, Carpenter and married to another Christian (cannot locate marriage) with a daughter Sophia bc.1810 Bath, Somerset and 3/4 children baptised at Etchilhampton 1816/7-1823. She died 1845 and he in 1864.
So two separate couples here for sure although the online trees suggest otherwise.
[Vashti seemed to be a name used quite a few times so not altogether sure there is actually a connection to India. In fact, googling reveals the name to be African, Hebrew or Persian.]
Annette