Good. now its time.
Go for @talhawaleed Expert opinion bro. Perform flush. Every required detail is given in post
https://www.pakwheels.com/forums/electrical-wiring-battery-lights/153379-maintaining-ups-car-batteries#post2525873
If you hvn't done it before. You will learn valuable stuff. As you are in lahore, you can easily get new electrolyte from prochem as @talhawaleed recommended. Call Rehmaat bahi Sale supervisior of pyrochem # 0301 8405723. Better get 30 kg can of prochem electrolyte for batteries for Rs.750 and save the rest for later use or you can get the bottles of 500ml ( a carton of 12 Liter cost Rs.930). Try to further negotiate the price.
Note: you don't need to take batteries to battery guy after putting electrolyte. Charge them at home using ur ups.
Best of Luck
Keep me updated
Best Joy
@talhawaleed Expert opinion:
If it has done two years, then clearly ups adjustment is good and formation of sulfate crystals wont be an issue. Anyway, if you have done so, then lets us know about the results. Flush, may its self will improve the backup time at this stage, since it?s been two years so it?s a needed exercise and it should be performed immediately once you feel that back time has started to go down. I hope, still all the cells are ok. Do use good electrolyte after flush.