The little female is somewhat underweight, as we noticed she was initially struggling to suckle, getting out of breath after a minute or two. When all three kittens went to the vet for a check-up it was revealed she has a slight heart murmur.
However, it need not be le fin du monde. She is now being fed by hand as well as by her mum to try to build up her strength and help her put on weight. It is working as she already picked up. In fact, today after this weigh-in on one of the kitchen scales she had gained eight grams.
Not much, but when you only weigh 246g then every bit helps!