Did you just now get them out of the lemon? All I do is rinse them off real good and stick them in the medium right away. Sherry says that is the trick with citrus - it has to be fresh. Every one I have done following her advice has popped for me 100 percent! Ask her when she comes back on, so I don't screw up her words. But I haven't gone wrong following her advice yet!
That is one reason I never order seeds off eBay anymore (citrus). Once they dry out they are dead. ~J