If they came by mail,from a greenhouse or a home center, it could be sunburn. They are not accoustome to the bright sunlight, they are not out in it. If this is not the case. we now have to look at how and where you planted them You should only plant the roots, the crown must stay exposed. The soil should be a good combination whether in a pot or garden. But with as hot and dry as it has been in some areas my concern is that they are drying out. They need to be thoroughly soaked every other day. This will help them to stay moist until the roots can do the job on their own.But don't float them, they don't do the backstroke as well as you or I do. Good luck