When I first started PoS I got about 65 GRA in 2 hours. This was about a week ago, since then I've gotten nothing.  Is it possible I started PoS just before everyone else did so I got lucky with my 65 GRA? I have 15000 coins

To get PoS block rewards you need to keep your wallet running. It is not necessary to run it for 24 hours a day if you have no many inputs (separate income transactions). Each input has its coin age that is started to count at the moment the tx had place. When its age reaches 10 days that input is eligible for PoS mining. The PoS mining is the process of searching the golden nonce for the block using eligible inputs, but the algorithm is much less CPU intensive than PoW mining. When the golden nonce is found for that particular input the block is solved. The block reward is added to the amount of the selected input and sent back to the same address being split into two equal inputs. Thus the coinage of the input is spent, the new two inputs has their coin age reset to zero and the process repeats. So, if you have not many transactions you may run your wallet for the couple of days each 10 days. But if you still mine PoW blocks that means that you regularly receive payouts from blocks itself if you do solo or from the pool otherwise. Then it is reasonable to keep the wallet running as much as possible. So you have to decide your strategy according to the situation.