Dear Dharmendra, Since how ...

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Dear Dharmendra,

Since how long you are using these membranes

Do you follow Cleaning / Flushing CIP of RO Membranes as per DOW recommendations on timely intervals

Did you check your Inlet TDS, if this is same or changed?

Do you have a Pre-Filtratioin System before hand also which is functioning well?

Did you check ORP Meter is funcitioning well if you are using NaOCl as disinfectant in pre-filtration? 

Does your SMBS Dosing Pump functioning well?

Does Cartridge Filter cleaned properly or needs replacement?

The most important, if you recently cleaned/opened the Vessel, then inserting membranes into the vessel is a careful job, each membrane module to be properly "Interlocked" and "Rubber O Ring" must be in place properly, otherwise, this could be the main reason for your issue.

Increase in Permeate TDS and Decrease in Reject TDS is a clear indication any of your Membranes has worn out/damaged/clogged thus not being able to perform properly the system as a whole. 

Kindly do the above checks first, then take out membranes. I am sure your problem will be solved.