Our 6 inch borewell in Uttarahalli, Poorna Prajna layout drilled in March 2012,
Total depth of bore well: 302 feet
Casing length: 44 feet
First source: 55 feet - (water yield : 1 inch)
Second source: 175 feet - (water yield :0.5 inch)
Third source: 230 feet - (water yield : 1 inch)

The driller informed that there are boulders and silt in the borewell and suggested to put the filter pipe. We had put the filter pipe of 5 inch diameter for entire 300 feet length of the well. This pipe is a PVC pipe with a slit at every 3 feet length of the pipe. We installed 1 HP 24 stage submersible pump at a depth of 285 feet as suggested by the pump distributor. We had got good water for around 2 months. Now we have started getting muddy water.

What is the reason for this? What does this indicate? What is the next step we should take?

Please suggest.
 
Regards
Vani