I had used my drone few times two months back and had kept it fully charged and did not use it as weather conditions were not good. I recently used it and charged again before use. I got only 6mins flight time. Is the battery weak?
it is not recommended to keep LiPo batteries 100% charged for long periods .. they should be brought to a storage voltage equivalent to 3.80 / 3.85 volts per cell.
most likely the cell is damaged. try as already said download it and recharge it a couple of times.