I have bought my TB48 5700mah battery on 26 April 2017, so about 3 weeks ago. After 9 times of charging, a full charge shows that the capacity of charge holding has now gone down from 5700 to 5529 and voltage at 26.05V. 3% loss of capacity over 3 weeks. At this rate of deterioation, I don't think the useful life of battery would hold for a year. If battery capacity drops down to 60%, the battery is pretty useless for flying, no one wants to worry about doing own a short flight and carry the same weight.

Should I claim warranty while I still can.

Have you cycled it yet? Try that.
Take it down to 5% then fully charge. See if that changes it's capacity rating.

Just to clarify, do the voltage seem balanced amongst the cells? Try Aeromirage's advice and let us know if the issue persists. You do have the option to send the battery to the AU Service Center for further evaluation and replacement, but you should give post #2 a shot. I'm assuming everything is up to date firmware wise, correct?

Thanks for the reply. However, what is the expectation about the charge holding capacity for the next 12 months. Yesterday, I run the battery down to 10% to recycle it but the reading is not good. Anyway, I will do another one today and see how it goes.

Keep in mind that the capacity in all its forms (percent, mAh,...) is a calculated, you can even call it a guessed, value. Even the voltage is only a secondary indicator as this depends on the amps you are pulling of course and ambient temperature.
The only real test is to drain the battery and check how much mAh you can charge into it. And even that test assumes that the same amount can be outputted again.

With these points in mind, a 3% deviation is no reason to be worried. If you want to know for sure, a complete discharge and charge makes sense. And a check if the single cells show anything abnormal - as suggested above. As a side effect of the discharge/charge procedure, the algorithms that calculate the capacity-remaining have numbers to base the calculation on, so will be more accurate.
What do you mean with "reading was not good"?

Keep flying and log your times to 30%. This will give you a better sense of how the battery is faring in terms of residual charge holding capacity. There is an initial drop in 'capacity' and then a steady phase. Note that the I2 batteries no longer display this 'capacity' measure - so there may be something to this.