I find it very discouraging that so few people have been taught to understand feed rations and how to adjust them in order to achieve desired rate of gain. Ag teachers need to step it up.
'grain' and 'hay' have absolutely no meaning in terms of the nutritional value of the ration that you're feeding. Is that a 50% TDN high fiber 'grain' mix or is it a 80%TDN high energy textured finisher? Is that 20%CP heavily fertilized Coastal hay or a 7% native hay?
Even without knowing the energy level of the grain you're feeding -which is most important- I would bet if you're only feeding 17lbs, then close to half of your heifers total ration is hay. Unless you're trying to hold one over- maintain weight- this should never be the case. With a calf of any weight, if half of their total consumption is dry hay, then you're going to be hard pressed to get much over a couple lbs per day gain. If you want a calf to really gain, the TDN% of the TOTAL ration needs to be over 70% with no more than 20% of the total ration coming from hay.
All the supplements in the world are of very little use until after you've adjusted the energy level of the TOTAL ration to meet your desired gain.