Krile, did you make any changes to Nevacoin's POS? My stake today was 2x lower than yesterday

Nothing is different until block 291111.
I do not control the network. If more/less people mine/stake I can not control that.
You will never have the same number of stakes as time goes by. Especially if there is a price increase, more people will stake and you will get less of the share.
That is not a bug, its a feature. A coin that is hard to get is worth more.