Yup as tuajia mentioned, nitrate kit is highly recommended so you can get a lid on what's going on with the tank.. Depending on the relative amount & condition of the recently added live rock, your tank could possibly be seeing a spike in nitrates, etc
once you cfm your readings, consider doing a 10% water change to reduce any elevated levels
meanwhile, continue to feed appropriate amounts where there's minimal accumulation of uneaten food in the tank...