It’s unfortunate that the harp manufacturers didn’t agree on a standard spacing like the piano makers do. The result is a lot of variation in the spacing on harps from one make to another and even from one model to another within the same maker. That’s the bad news. The good news is that with practice you can learn to adapt almost instantly. Try to play as many different kinds of instruments as possible on a regular basis. Just sit down for a few minutes and play an instrument that you haven’t played before. With time you’ll learn to adjust immediately and won’t have any problems.