LRP batterys swollen

[reg]

Hi,i bought two LRP 1s 6700 batterys,
they are showing signs of swelling,they were new and not close the end of the life,iv only ever charged them up at 4 amps,
what would make them swell up,i could understand if they were old and id abused them but iv not,when i use them,i always use one for the last round of qually,then the other for the final so they both get put away having run at least 5 mins after a full charge,one deffo had more puch than the other one to,
thanks
Mark