500 mile old pair of 140mm fox forks should have had about 70 psi in them,i havent checked them for a while,first off road ride today in 2 months and they felt soft got home only 10 psi in them, what is my next step, just pump them up and dont worry or back to shop??

Shouldn't go down that quick. Check the valve core first.. You'll need a schraeder core tool. take the core out, clean it and replace. You can always put them in the bath to see where the air is coming from!

Air back in, do weekly checks.