I had 3 crown buildups with pins. a week later i was told all the of those need root canals. is this normal?

Because : Your teeth were so badly broken down that they needed building up, it is likely that their pulps (nerves) were already compromised. Your dentist tried to restore your teeth with the hope that the pulps would survive. Unfortunately, you will need root canal therapy in order to save your teeth. This was unlucky but not unexpected.

Crown Build ups: Small pins can help replace missing tooth structure and provide support for a restoration, but in a severely broken down tooth, they cannot replace a post and core, and for that you need root canal therapy. Your dentist attempted to avoid root canal therapy, but reconsidered that decision once the pins and buildup was placed.