Rubbish - Growmore is a standard, balanced NPK feed, does not contain excessive nitrogen, but has a fair amount, and I use it most years in baskets at the initial plant time, if I'm re-using old compost. However, I wouldn't use growmore granules for baskets any other time - use Miracle Gro general purpose liquid feed, or a flowering plant liquid food, instead. Another one on the list of things people say as an excuse - I've heard a fair few in my time, lol.
The only proviso though, is that your friend didn't use Growmore granules every week in the basket - they should only be used every six weeks, so if he was doing it more often than that, then that might have caused problems.

oooooohhhhhhhhhhhhh i want to swear.What planet is this specialist on.??

You can only do what it says on the pack.
This specialist cant be qualified that much , for dishing out that sort of information.
I would change the place where i get the hanging baskets from.

Well in fairness, he probably didn't know what the cause was; to mention it a year later isn't really fair on the supplier, complaint should have been made at the time. And sometimes something happens, like vine weevil, etc., which destroys baskets, so he's just made something up that fits the story - if he knows his onions, he knows he's lying, if he doesn't, he may actually think its true. The latter of those two options is far more worrying to me.

sounds more like he didnt want the blame and money was doing the talking to me . call me old fashioned but it seams to be the way of the world these days.

Thanks for your comments. I intend to quiz the neighbour and the basket supplier about this and if I can throw more light on it I'll post another question.

ok mate good luck .