UPS batteries performance reduced

HI

i bought an inverter(UPS) 1600watt. with 2 batteries. 10 months ago. it worked like charm. now the batteries finish relatively quickly and its degrading day by day. there is no problem with the water. i've added some water only once and never again as the solution never reduced.

shall i replace the acidic solution all together or its the plates causing the problem?

advice needed

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