Curing the genophage completes "Priority: Tuchanka", so you should be able to complete "Heating Unit Stabilizers" and "Book of Plenix". Once the Citadel attack is thwarted you've completed "The Citadel II", but you should be able to take care of "Cerberus Automated Turret Schematics".
Though it's not one of the missions you've listed I've had a similar issue handing of the ciphers for "Citadel: Cerberus Ciphers"; when this happens I follow the following instructions to get the quest back on track:
"Note: You may be unable to interact with Dellk after buying the ciphers from the Spectre terminal. Just head to any other Presidium level, then go back to the Embassies and he will be selectable again. Alternatively, saving and reloading the game should fix it as well. This doesn't always work however (Xbox/PC)."
thanks for the info but on 2 of the side missions, not the book, I should be able to buy the items at the Spector terminal in the Spector room where the shooting range is. But those items are not there unless there is another terminal I am not aware of.
Thanks,
Russ
Following sundance31us's link shows this text with regards to acquiring the Book:
Scan the volus homeworld of Irune in the Aru System of the Aethon Cluster to acquire the book. The Aethon Cluster will not appear on the galaxy map until after completing Priority: Tuchanka.
Return to the Presidium Commons in the Citadel after obtaining the item, and speak to the Angry Accountant. You will receive an update on the Citadel Defense Force War Assets.
There is one other location you can access the Spectre Terminal, but it has a 10% mark-up price, and that is on the Normandy, in the shuttle bay, in the Kiosk on the right. I use that to review what purchases are available, then go to the citadel to those appropriate stores to make actual purchases.
