Donna, I'm pretty sure the enhancing sealer won't penetrate the porcelain tile. Tile/grout manufacturers always recommend that you use a cloth or sponge to wipe up any excess sealer if any gets on the tiles. Even tho the sealer can't penetrate the porcelain or ceramic, it can dry and look hazy or dull if not cleaned. I've already put enhancing sealer on my porcelain tile. It brought out the color of the grout and didn't affect the tile in the least. Mari, are you tiles natural stone or porcelain/ceramic? The information above is for the OP using porcelain tiles.

There should not be lippage (height difference from tile to tile). This is pure installer error or a lack of education in how to set tile. A good tile man with have a 2' masons level to lay on the tiles as he is installing them to ensure there is no lippage, and if their is you remove or add thinset as needed for a flush transition from tile to tile. This may be repairable but in the worse cases it can end up being a large job pulling up and resetting enough tiles to get everything flush, and if enough tiles are lipped to a low or high spot in the floor, a considerable amount of tile may be needed to be removed and reset to rectify the problem. I am not saying the latter is the case with your installation, but i have seen it that bad before. The "haze" is called efforvescense and occurrs in portland cement grouts that are mixed with too much water added when the grout was mixed. It should be regrouted.

There are acid cleaners you can use. I'm sure someone here knows but you can also check over at John Bridge Tile Forum. I think they say start with a mild vinegar. Forget if it's straight up or diluted. (applicable only to other stones and tile) Did you seal the onyx first? Doesn't that have little cracks in it, that is, some porous areas? This post was edited by snookums2 on Fri, Apr 19, 13 at 20:49

Following and will share this with my daughter. She has white hexagon tiles that have the haze, so not as noticeable but still annoying. Elbow grease and regular cleaning did nothing (floor installed a year ago) so will give the magic eraser a try and then it sounds like Oly's suggestion will do the trick. Thanks.