Need help to set right the borewell issue


We had got a borewell dug in 2010 which was giving good water since then. Few weeks ago we got little muddy water. Now when we are switching on motor the MCB reading is 15 amps (used to get water at 15amps, 200v earlier) with no water. After a while it drops to 13 amp again with no water. The voltage is steady at 200v. What can be the possible reason for this? Please help