What has happened to my Chrysanthemums

I bought 3 Chrysanthemum plants about 2 weeks ago. Two I put in one container, both still in their original pots and the 3rd I put (still in its original container) inside another pot.
You can see from the photos that the 2 together have developed some sort of petal disfiguration. The worrying thing is that some (most) of the new developing buds are going brown and not opening. Were this not happening I might be excused in thinking that the blooms had bloomed and were over. The plant that sits on its own is very healthy (see last photo) and none of the blooms are anywhere near over. I water and feed all plants regularly having never let them dry out. The only difference between the two is that the healthy plant sits right next to the window and the others are in the middle of the room but that said the room is very light.
Can anyone help me - I have seen in my RHS encyclopedia something called petal blight but apparently it is quite rare?!

 

Hi Charlie... sad that.....potbound more likely, apart from the following.I suggest cut the plants back,down to some strong leaves, pot in bigger pot separately, feed on high potassium, like Phostrogen, put them outside. One of the other reason, lacking proper light,they may have been forced for a special date and then sold on....as they do lol..and you should have them in flower again soon.
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Ladybird

 

Charlie another chance is, it could have dried out at some stage, before you got it..Chrysanths are very tough.....Remove flowerhead on the 3rd plant each low down, after finish and keep feeding it weekly, a pinch dry to the pot and water in it may never stop flowering then.

Will email you to show one of Chrysanthemums...still not found, how to upload here, can do it in other groups..
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Ladybird