Yeah, as others have answered what I was going to say.
So sadly your player A and C didn't receive the JS training (unless you've also played them as either SG or SF in other games when they weren't playing as PG).
So just make sure, from now on, training only happens on friday. You can change to whatever training you want to give AFTER the training update is done. If you change PRIOR to the training update, your effort in making your players play at particular position will be useless because that skill you've changed to, is the skill that gets trained.
I hope you're clear now.