Viola middle D is sharp and Violin high A is flat
The subject pretty much says it all. By high A I mean the A on one ledger line, aka A5 (the bottom A on a piano is A0)
This is just a problem with the sample library being improperly produced. There is an easier fix than re-recording however, and that would be to simply fine tune the samples digitally. The amount that they would be shifted is very small so it wouldn't noticeably affect the timbre.