It's nearly impossible to diagnose problems without more information: weather conditions, rhododendron variety, wind, time between planting and the symptoms, reasons you believe "growth tips" are dying, etc., etc.

The scenario is not unusual. In a nursery the plants are usually planted in a soil mix that can be watered every day without being too wet and causing root rot. This means it is a mix that dries out rather quickly. When people buy them the watering regimen changes and sometimes the root ball dries out. If this happens, it is very hard to get the root ball wet again. It becomes virtually waterproof. You can water all you want and the root ball just sheds the water. The best fix is to dig it up and soak the root ball in water. If in fact the root ball is light, hence dry, then soak it for a couple hours and replant it. Mulch it good and water whenever it looks like it is starting to get dry. Young plants may need protection from direct sun and wind for a while, especially if they are coming out of a greenhouse.

They need excellent drainage but they also need to be kept moist. This isn't trivial.

A second very common problem that doesn't show itself as quickly is that the root ball must be opened up on container grown plants. Rarefind Nursery has a good description on a good way to do this. The important phrase is "Don't Be Timid". They have an illustration of how to make a deep x cut in the bottom of the root ball and then spread the roots out over a mound of soil in the planting hole. See link below.

Other possibilities are:

The plants may have been left in a car where it got hot and cooked them.

The plants may have gotten frost bitten.

Herbicide sprays.

Road salt.

etc.

Here is a link that might be useful: How To Plant (Rarefind Nursery)

rhodyman, Thank you for the link. I tried roughing up the outstide, but it was hard to get anything loose. I would have never tried doing those deep cuts if I had not seen the link you provided. I think I will pull them up and follow those directions. Thank you so much for the help.