Performance issue with update query after adding index - mysql

Question

I have added the index to my update query and by adding the same query start taking several hours to complete the process.While without index its completing in some minutes i have added the index to faster the process but it became very slow exactly opposite to my desire.
Below is sample code snippet of my code.
Cursor c_updt_stg_rsn is
select distinct substr(r.state_claim_id, 1, 12), ROWID
from nemis.stg_state_resp_rsn r
WHERE r.seq_resp_plan_id = v_seq_resp_plan_id
and r.submitted_claim_id is null
and r.filler_2 is null;
BEGIN
OPEN c_updt_stg_rsn;
LOOP
FETCH c_updt_stg_rsn BULK COLLECT
INTO v_state_claim_id, v_rowid LIMIT c_BULK_SIZE;
FORALL i IN 1 .. v_state_claim_id.COUNT()
UPDATE /*+ index(STG_STATE_RESP_RSN,IDX2_STG_STATE_RESP_RSN) */ nemis.stg_state_resp_rsn
SET (submitted_claim_id , filler_2) = (SELECT DISTINCT submitted_claim_id, sl_group_id FROM nemis.state_sub_Resp_dtl D WHERE
(d.state, d.type_of_claim) in (select distinct state, type_of_claim
from nemis.resp_match_state
where seq_resp_match_table_level_id in
(select seq_resp_match_table_level_id
from nemis.resp_match_table_level
where seq_resp_plan_id = v_seq_resp_plan_id))
AND resp_state_claim_id LIKE v_state_claim_id(i)||'%'
)
WHERE ROWID = v_rowid(i);
IF v_state_claim_id.COUNT() != 0 THEN
v_cnt_rsn := v_cnt_rsn + SQL%ROWCOUNT;
END IF;
COMMIT;
EXIT WHEN c_updt_stg_rsn%NOTFOUND;
END LOOP;
CLOSE c_updt_stg_rsn;