Spine is often marked right on the arrows you get. Especially Terminators. IE 4560 or 6075. These numbers designate the suggested weight range to shoot them in---60# to 75# usually at 29". If you vary much from the length then you can interpolate a bit in your choice of arrows. In your case I would shoot the 6075 Terminators whether you shoot them at 60 or 70#. With carbons, stiffer is always more forgiving.

Now you get into higher quality arrows they are not always marked like this. For your setup, were you shooting Carbon Express CX you would want a 300. Easton should be about the same---300. Blackhawk Vapor would be a 5000. Gold Tip would call for a 5575 arrow. There are usually charts on the boxes they come in to help with choice.

Hillbilly, just for info how big a guy are you? It's not written in stone and varies, but a 30 inch draw is about what a guy with a 75" wingspan uses--if his drawlength is close to correct. When shopping for a new bow I'd suggest you visit a local proshop and get measured for correct drawlength. One of the best waya to get a start is to measure your wingspan and divide this by 2.5. Most guys draw about 2" longer than they should if they are interested in accuracy.
Being as you have a 70# bow and are shooting it at 60# suggests to me that you are comfortable with 60#. This is all that is necessary for anything walking this continent. So for your next bow I would look at 60# max. It'll be easier to draw and shoot which can let you shoot more often, longer sessions so that you can work on perfecting shooting form without struggling with the bow. You should NEVER have to struggle with a bow--especailly that firstand maybe only shot at a critter.

I got no idea about the arrows you are presently shooting. Never heard of them. They are probably some cheaper arrow made for one of the Walmart/KMart stores. I know everybody has to start somewhere but as time goes on I would definitely upgrade to better well known arrows at the very least. Then you'll know what you got.