lipo puffing advice

hi guys i need your advice.
i bought 2 zippy-r lipos about 2 months ago but because i was waiting on 6.5mm connectors fom my LHS i haven't used them until last week.
i have used them about 5 times and i have had some concerns. they puff like a mother and one of the packs remains a bit puffy even when it has cooled and been left for the day.
i payed £80 for the pair ~ $132
i am dissapointed as i thought they would offer amazing perfomrance and i certainly wasn't expecting them to puff.
they are 14.8V 4500mah 21/35C lipos so i used them in parallel so i thought they should be up to it. i have contacted the seller and let him know but i feel like an idiot leaving it so long to test them...

what should i do