A disclosed system includes a plurality of ion selective fiber sensors configured to measure treatment concentration variance, and a computer in communication with the plurality of ion selective fiber sensors. The computer determines treatment coverage for different downhole zones using information received from the plurality of ion selective fiber sensors. A disclosed method includes collecting data from a plurality of ion selective fiber sensors configured to measure treatment concentration variance. The method also includes determining treatment coverage for different downhole zones using information received from the plurality of ion selective fiber sensors. A disclosed downhole treatment management system includes a data analysis unit that collects data from a plurality of downhole ion selective fiber sensors configured to measure treatment concentration variance, and that determines treatment coverage for different downhole zones using the collected data. The downhole treatment management system also includes a treatment control interface in communication with the data analysis unit. The treatment control interface updates treatment operations using treatment coverage information determined by the data analysis unit.