Hi,
All of your data sources master data sources.
So as my guess most of the data source fields will be pulled from master data table.
So take source team help and find base table.
Example - 0PLANT_ATTR, for bw info object 0PLANT - related ecc field is - WERKS.
For WERKS master data table - MARC.
Like that way you can all master data tables of your info objects at source side.corss verify data source fields and base tables fields.
Another possible,
run your data source at RSA3 and debug it.
you may find source tables.
Take source team help. might be helpful.
Thanks