Thank you for taking the time to answer my questions, I appreciate the information. I'm glad your vet thought her weight and body condition was perfect in February when she was spayed, this is a good sign. Cane Corso's do tend to be very large dogs, and it's important to realize that their size and weight can vary. As you're aware, there are set standards for height, weight etc. Sometimes pups from even the best breeder and the best stock are a little different from those standards. And, as I'm sure you know, females do tend to be smaller than males. Pups generally tend to be very close to their parents in terms of size and weight, but again, natural differences can occur.
Based on the information you have given me and the fact that your vet did not have any concerns about her weight, I think that she is naturally lean. Some dogs tend to gain weight after they are spayed, due in part to a reduction of hormone levels. If your guess of 85 pounds is correct, and based on her age, she has in fact gained some weight.
One thing that you should consider investigating is whether Bella has any intestinal parasites. You have to have your vet check her stool for parasites, and have her examined for overall body condition. The reason I am concerned about parasites is because she is not on a monthly heart worm preventative. She needs to be on this, every month to prevent heart worms and intestinal parasites. In heavy infestations, intestinal parasites can lead to low body weight. You cannot safely deworm her without having her seen by her vet. There are a range of different parasites that require specific and different dewormers. Some parasites even require antibiotics in addition to dewormers. In order to determine if parasites are a contributing issue to her weight, your vet needs to see her and examine her stool. If parasites are present, appropriate medicines can be prescribed. Your vet can also prescribe some heart worm preventative, which is not available for purchase over the counter.
If your vet agrees, after examining her and weighing her, that she is in fact underweight, steps can be taken to rule out illnesses and parasites known to contribute to low weight. There are some foods that are higher in protein levels that can help dogs gain weight, BUT they should only be started under the supervision of your vet since large breed dogs can have issues with these diets in terms of bone and muscle health.
If your vet is still pleased with her weight and body condition, that is great news. Large breed dogs can be prone to orthopedic problems with their long bones and joints. It's always best to keep them on the lighter side to ease stress on joints. I have an american bulldog, and he's weighing in at about 100lbs right now. He's a little heavier than I like, and his optimal weight is about 95lbs. He has weighed as much as 110lbs, which is too much. His parents were 85lbs (dam) and 105lbs (sire). When I first got him, I wanted him to be huge! I am happy with his size and weight, because he is healthy. He is also dealing with allergies and needs oral and injectable medications, and this is cheaper when he weighs less.
If you have any further questions, feel free to let me know. Best of luck with your Pretty girl :)