If you're using smartpak, maybe you could look at finding a supplement that is more "well rounded" to achieve what some of the individual ones are doing.
I switched Whiskey to SmartFlex senior, which gave more benefits and eliminated the need for me to give him the MSM and probiotics since they're included in those pellets. He was good before, but he's like a new man now, and I feel that it saved overall. Check the ingredients, might have the amino acids in there too.
Is Lizzy pretty underweight or a really hard keeper? Between hay, beet pulp, alfalfa pellets and grass pellets, maybe you want to cut one out and experiment? I'm certainly not a nutrition expert so I'm just thinking out lout and curious what others have to say as well.
Whiskey is 18. He is on a round bale in the paddock, and gets one scoop twice a day of Purina Ultium/Sweet feed mix (which includes beet pulp, and he likes the texture of sweet feed blend instead of straight pellets) which runs me $39/month. Then he gets SmartFlex Senior and Cool Calories for supplements at $49/month. He's maintaining a healthy weight.