RO Membrane Damage

We have a 3000 lph RO plant. We recently changed the first membrane due to high TDS, and once again the new membrane, which is in first, got damaged within one month. TDS rise in the entrance of the first membrane. What is the cause? Every pressures is normal. Feed presure 9.5kg Feed water reject comes around 5200 lph Product water flow 3000 lph.