Begonia Problems

I have received my trailing begonias mail order. Got 9 , they are dropping like flies ! The leaves go black at the edges , then the stem just falls over - thud ! I have isolated them given them a spray with bayer fungicide , and sent a complaint Email to the supplier . I have tried to look the complaint up , as I have been growing Begonias for seven years without a problem . I thought it would be stem rot but no one mentions the leaves going black at the edges

TIA

 

Cold and wet, was my first thought....

 

Too early and too cold is my guess. Mail order is a bit hit or miss for gardens north of the Watford Gap as many of the plants supplied via mail order are grown for southern climes which can be at least 4 weeks ahead of us up in the north.

 

Thanks John , Freddy , I always keep my Begonias lightly watered until they are established . They are kept in the house at the moment and Mrs H keeps the temp within 1 or 2 degrees of the Borneo jungle .
The pic shows theone that died today. The main stem had died 2 days ago . This sub stem looked healthy - then went like this overnight !

 

Thank all for the advice , never had this problem with Begonias before . I'll be more prudent wih my watering , and make sure I use copper based fungicide when I pot them up.

 

Thompson and Morgan have just phoned me . They are replacing all my Begonias , sending them out first class today. Super service from T and M again 10/10 It is a lot warmer now so they won't get a chill in the mail . Also I will be careful with my watering. I do bottom water a lot of plants , I am now going back to top watering as I think it is very easy to over water with the first method.