Help - Is Harry on his way out?

Hi everyone, I'm hoping that someone has some wise words out there that may hopefully prepare me for what's going to happen next with my poor Harry.  I acquired Harry by accident back in April this year...  he surprisingly turned out to be a Cockerel (I used to call him Hatty!) plus he really is a meat bird. 
I've posted on here before and been given some fabulous advice on what to expect as he's a meat bird ie he wont last very long.  But I just want to make sure I'm giving him the best shot as he's been such a star. 
A couple of days ago I noticed his crop going quite purple - this isn't unusual as if my OH goes in to feed him in the ams Harry really does take humbridge and gets in a right old tizzie attacking his wellies etc... this always makes him a bit purple for awhile but then he goes back to a lovely red colour (Harry not the OH).   However, this time it was first thing in the am, it was me opening the coop, he was purple already, he was a bit subdued plus he wasn't that bothered with his food (unheard of!).  Today I went to let him out in the am and he was doing his normal crowing in the coop before i got there... I opened up the door and he was a very deep purple and wasn't interested in his food again. I did bring up a fresh corn on the cob for him which he did come out the coop to eat. 
I've been at work today but my OH has been up to him and said he's just been sitting in his usual place under the tree most the day.  When I went up to shut him up he was in his bed as usual and still looking a nasty deep purple.  there's no discharge from his ears, mouth, nose, eyes... his breathing is a bit laboured but to be honest it always is as he's such a big bird.  I did notice he hadn't poo'd very much in his coop last nite?  His poo otherwise is looking normal.  I last wormed him about a couple of months ago so thought i'd worm him again plus I've got some really good multi vitamin to go in his water..
Do you guys think I'm right in thinking this is his heart packing up and I should just be making him comfy?? If so any other suggestions on making him as comfy as poss...
Or
Do you think I should take him to the vet?  Altho I am a bit worried the stress of that might be the last straw??   
I'm so attached to the old fella and really dreading the day he goes but if I can prepare myself it wont be such a shock.

Hi Orchardlady - thanks for your kind words... Harry died early hours of this morning.  I went to let him out at 7 and he was face down in his supper bowl... Bless him.  I'll miss him dreadfully but I know I gave him the most spoilt comfortable life.  I rescued him from a survival training weekend where they were going to eat him back in April this year.  So I can console myself that he had a lovely time in the lovely summer sun, wandering about the garden.... 

Ahh, I'm so sorry to hear that Harry didn't make it but as you've said he's had a good life with you.

Im so very sorry for your loss. Harry is now in chook heaven with our boy Monty and countless nubile young hens for his amusement. I have to keep thinking that there is a chook heaven, it makes the grief bearable.
It sounds as though Harry had a fabulous life with you, you'll miss him, the peace and quiet is deafening!
Good Luck for the future, and again, condolences.

Mary.

So sorry about Harry but it sounds as though you gave him the best life possible and you should be very proud of that.

Unfortunately meat birds are bred to eat and put on weight and this does put extra strain on their hearts.

Oh dear, so sorry to hear about Harry    He had the best of life with you though and he will have enjoyed himself with all the freedom and tlc that you gave him. Very sad though and it does knock you for six I'm afraid