Hi everyone, thank you for the suggestions. He is actually currently on SmartCalm Pellets, but I have upped his dose a bit. I had cut it due to a nutritional analysis I did, but have since put it back up to the maintenance dose.
We also think that the change in pecking order in his field recently has added to some of his “changes.” A horse that was the “boss” passed away a few weeks ago, and now the field is experiencing some changes in hierarchy. Namely, my pony is trying/actually is number one, and the horse I mentioned here is sort of number 2 in that he follows my pony around all the time. I think it’s a combination of these things as well, but I will be trying to supplement fat using some of the suggestions rather than upping his grain to get that weight on. He also is receiving a lot more hay.