Fire Blight? - Apple Tree

[Rpomi]

Hi everyone,

 

I have a Gloster Apple Tree that was fruiting really well up until 3-4 weeks ago. The leaves started to go brown like in the attached images and the fruit just stopped growing so I picked the fruit off to try and help the tree focus on itself. The only thing I can find online that might be an issue is fire blight? But the treatment looks severe and to be honest if it is then the tree might already be dead.

 

If anyone has any ideas on what it could be, whether the tree can be saved or whether it's likely dead it would be much appreciated.

 

It's in a big pot, we're in a dry and sunny area but it's watered frequently. I also have 2 cherry trees and a plum tree of the same age, in the same size pots which are all doing quite well.