We actually feed our performance horses (racing/jumpers) Tribute Essential K as well. They are all thriving. It's mean for horses of all ages, types and training levels. Tribute all round is a good feed.
We chose the Essential K because it's a ration balancer, specifically because of the high protein content and you feed less than most complete feeds.
I have her on that at the moment but becuz she's only 6 and still has growing to do and now being in foal was told by Tribute person been talking to said she be best on growth, but I also have body build threw elite three, it's good for mares in foal or lactating and such but I'm just trying to balance at the moment and not 100% sure what's to much protein and not enough
I'm not 100% sure of your question, but the protein requirements of a pregnant mare change as the gestation continues. A specific feed at 16% might be okay if given in the right amounts, but that may cause issues with other nutrient levels.
For example, protein requirements for a 500kg pregnant mare go from 660 g/day in early pregnancy to 866 g/day during the 11th month. Calcium levels go from 20 g/d to 37 g/d in the same time period.
If you aren't sure whether or not it's suitable for the stage of pregnancy your mare is at, ask the feed company. Many feeds made for pregnant and lactating mares are designed for later stage pregnancies.