The most common mistake new users make is running the atty to dry. It COULD account for most of the symptoms. How do I know? Been there done that.
Where did you get the two different kinds? There are 2-3 kinds out there. The true Joye the dse and maybe the disposables. Could be a couple of more but I haven't heard of them.
My original 510 was from Janty and they still work and are my favs. I ordered spares from them and got the ones with the wider brass ring which were worse. Bought the Evo and the attys came with the same smaller brass ring (sorry I know that makes no difference in their performance