I had 3 buddlia "buzz" delivered from a reputable garden centre and the same thing happened to mine .I contacted them with the problem and they immediately sent me 3 replacements free of charge. The new ones are doing very well and the 3 first ones are surviving although look sad for themselves, but I will persevere. Perhaps you should complain?

I am not too concerned about the larger two , but the smaller plug I have my doubts . I got that particular one from e bay.The seller has not answered my question ,which I have repetitively asked .But I will e mail and ask for a replacement .