Hi! I have a newly built house and did 90% of the flooring myself. My problem is the ceramic tile in the kitchen. This is a high traffic area between the sink and stove area and about ten tiles became loose after the first year of installing the floor. I pulled them up and scrapped the old mortar off and reapplied the tile staying off them for 24 hours. After about 6 months they are once again loose. When first laying the tile I put durarock down and used thinset purchased at Home Depot. How can I get these tiles to stick to the floor?