That is a bit odd, but it doesn't mean you have lost them. Give then a bit longer. The only thing to do to check for sure is to dig one up and see if it has made roots, but you would have to find it and that might disturb the row too much.
If it has rotted, there is nothing you can do now. The rest has grown OK so it isn't anything you have done.
I would wait and if nothing happens, buy some spring planting garlic in January/February when it appears in the shops and replace the rows that have failed.
