Wilting Rhododendrons

So, here's a puzzle.  I bought about 20 rhododendrons from 3 different stores.  I planted them immediately, with my customary care of big holes and lots of compost, and for a couple weeks they looked great.  But they started putting on an awful lot of top growth for newly being newly planted.  Then they started to wilt during the day.   I scratched my head for awhile and blamed everyone including myself.

 What I'm thinking is this:   I think the growers gave them too much food and they've overgrown their root structure.  They are wilting off branches to save themselves.  I just went around and pruned off most of the new growth, saving only larger leading branches.

I must admit, I've grown rhodies before and never had this problem.

Whatcha think?