Poo advice please!

[Mouseinahole]

We have 3 cats/kittens. One will be one on Sunday and the other two (unrelated) are 7 months old. Two BSH boys and a Thai/Korat girl.
We recently got a new carpet in the living room. All was well for a couple of weeks then Colin (BSH boy aged 7 months) just pooed on the carpet right in front of me!! There are 3 clean litter trays a few feet away which he has always used. The poo was normal consistency and he is not ill in any way. He is his usual self in every other way. I shouted at him and took him to the litter trays but I'd like some advice on how to stop it happening again.
People on here were lovely when I first got the cats so I've attached some pics of Trevor, Colin and Mavis. The first pic is Colin the culprit then Trevor then little Mavis mischief personified.

[Toddlerteaplease]

No advice but omg they've grown! They are sooo gorgeous. Maybe he's telling you he needs to come and live with me!

[Mouseinahole]

Observe said corner! Tinfoil, lemon slices, cinnamon and favourite toys there now. New litter tray and different litter bought. Colin has had a good sniff at corner and wandered off towards litter tray. We shall see.

[Toddlerteaplease]

That's what I've done too my sofa to stop one of mine peeing on it. It's got my her favourite cushion and her bed on it. Seems to have done the the trick. Hopefully it might have just been a one off.