Add a buffer around a point in a ternary diagram

Question

I have used ggtern to create the following ternary diagram:

library(ggplot2)
library(ggtern)

NP_data <- data.frame(
  SE = c(15, 18, 57, 32),
  EE = c(52, 70, 8, 26),
  ES = c(33, 12, 35, 42),
  Perc = c(1, 1, 1, 1)
)

 MObj <- c(40,30,30,2) 
  
  NP_Mobj <- rbind(NP_data, MObj)  

#Add this point into the IWRM triangle:
  
reference_triangle <-  ggtern(NP_Mobj, aes(
    x = EE,
    y = ES,
    z = SE,
    color = Perc
  )) + 
    geom_point(size = 5) + 
    theme_showarrows() +
    labs(yarrow = "Economic efficiency (EE)",
         zarrow = " Environmental sustainability (ES)",
         xarrow = "Social equity (SE)") +
    scale_colour_gradient(low = "yellow",
                          high = "red") +
    theme(legend.position="none")       +
    theme_clockwise()

I want to add a buffer area (+- a percentage) around one of the points, so that I can visualize which points are closest to the reference point (pic shows an approximately +-20% from the yellow circle within the hexagon).