Kobo and Diesel: my books are not there right now

I had my books on sale for a while at 99¢ each, but now they are back to $2.99 for No Safe Haven and Tribes, while The Sixth Discipline stays at it loss-leader price of 99¢.  When I was checking to see if this change on Smashwords had been passed on to other retailers, I noticed that Kobo and Diesel appeared to have dropped my books. I am trying to resolve this situation. I don't get a lot of sales from those stores, so I don't know how long they have been missing.