He is still skinny yes needs more weight yes. Tips- add some canola oil to his feed it rally helps. I have a 17 year old arab and he was SKINNY maybe through him an extra flake or 2 or try to get out to graze him often. Maybe add a little more of the grain. Double check with you vet before changing quantity of food. The oil though is not necessary for a vet but it never hurts to let him know what your doing. Also flax seed. Its conditions the mane, tail and coat and also strengthens the horses hooves. We give that to my OTTB. Ask around for specific measurements and stuff. You can give the flax to the horse whole but they get more nutrients out of it if you grind them you in a blender or I use a magic bullet.