What happened to Jane Jarrett Carnes and her sons?

The Isaac Carnes family was living in Waterville, Marshall, Kansas 1 March 1875 (Kansas State Census). Two sons have been born since the 1870 census: David O (4) and Gilbert (2). Another son, Alonzo, is born 16 Oct 1876. Alonzo’s death record says that he was born in Clay County WV but this may not be accurate. He may have lived most of his 81 years in WV but actually born in KS and the informant did not know.  I have found several of Isaac and Catherine’s children living in WV with relatives on the 1880 census. Something tragic must have happened between 1 March 1875 – 1880. Isaac and Catherine must have died.

1880 Census:

David - living with Benjamin and Mary Coddle in Big Sandy, Kanawha, WV as an adopted son

Gilbert M - living with Clayburn and Charlotte Pierson in Henry, Clay, WV (Clayburn and Charlotte were living among several Samples households in Clay County on 1860 census so I have a hunch that Charlotte is a relative of Catherine, sister perhaps?)

Virginia and Alonzo -are living with James H. and Mary Carnes Mullins in Union, Clay County, WV; Virginia is listed as a ‘servant.’ A Franklin B. Nichols is also living in the household as a servant working on the farm.

There is a Clark Carnes living in Arkansas with his wife Delila and son Swan. 

There is a Jane Carnes that was born in 1806 and died in Greencastle, Indiana 1 May 1889. I know she had family that moved to Indiana but I don't think that there is enough information to say that this is the right Jane.