I was just asking. I more wanted to be sure I wasn't under feeding. He is not a "kennel" dog he is out all day while we are at work so he does get a lot of exercise. What would you recommend to feed?
Without knowing the parents and the breeder it is just hard to tell. I asked about the puppy food because switching to adult food before 4 months can often lead to a slower growth in setters. Slowly tapering off to adult food by 4.5 months is suppose to help avoid joint issues in setters. Not really a weight issue but a rate of development issue. We have had two dogs we acquired after 6th months from bad homes. Both were great dogs, but both suffered issues early in life. I've always theorized that was a result of poor quality food and improper management of nutrition during their growth years.
We have always raised our springers and setters as free feeders. Has never been an issue until after they are retired. And then it's been a bigger problem getting them to eat enough as they hate the senior dog formulas
(have tried dang near all of them). Our two dogs now are having issues. But, both are living beyond the age expected for the breed. Due to a nerve sheath tumor one is too skinny and not wanting to eat. The other is breaking down quickly
(the one we expect was abused and fed garbage food as a puppy). So we switched back to active dog foods and one has gained more weight than wanted and the other is still way too light. Feeding separate foods but it's still a battle. We expect this time next year we will have neither with us so we are much more concerned with keeping their quality of life "happy" and less concerned with the results of their weights or diet concerns. Mom and Dad are emotional wrecks but the puppy/girls are happy! That is all that matter to us anymore

Five months old and 35 pounds I expect is right on course. He could end up being a small for breed size. Which to me would be great! As hunting dogs I like the ones that end up on the lower side of the breed scale. I've always thought they had more endurance and command in the field. Especially the small bred GSP. In my teens I hunted chucker with a fella that had a small bred setter and he was a dynamo! He was not a runt, just bred small. My little springer sweetheart we have now was probably the most outstanding upland dog I've ever seen work birds. Smartest, quickest and most natural hunting springer you will ever see. We hunted her dang hard and she never once quit. The last hunt she wanted to keep hunting even through the pain. I had to carry her out to go potty for two days afterward but she was still begging for more hunting. Best puppy daughter I man could ask for!! Sure wish there was a pill that would turn her into a puppy again

If you continue to have growing concerns I wouldn't hesitate to see a "Good" vet. Ours claims that puppies are the spice of life! As such she never would charge us a for a simple checkup and question visit. Even after one year the visit charges were minimal in price. Often the peace of mind was priceless.