My P3 4K battery has about 12 charge cycles on it and is about 6 months old.  I recently tried to fully discharge the battery according to the DJI recommendations.  After discharging the battery became puffed and will not charge.  Has anyone else had this happen?  The battery has NEVER been flown below 30% and is always stored at the storage charge level.

There is only a 6 month warranty on batteries.  If you're still under that, even by a single day, send it back immediately.

Sorry to hear this ...

But where does DJI recc'd after 12 charges to fully discharge ?

In fact they have never advised to FULLY discharge a LiPo battery - that is DEATH to a LiPo .....

They used to recc'd Deep discharge after 20 cycles ..... which is to 3V per cell (12V total), which is a different matter - what is termed zero level but in fact is lowest safest level of discharge.

DJI control board is supposed to stop discharge at about 3v per cell - but trouble is as I found out after dismantling and checking actual board etc. - the board regards 12V rather than individual cell 3.0v as its terminator ... I found one cell well below that. I suspect that is what happened to you.

As other says - IF you have any days left on warranty - GET IT REGISTERED for return NOW !!

Nigel