Adding percent increase/decrease labels comparing to a control in ggplot2

Question

I need to compare my treatments for each day to the control and then add percent labels to the top of the bars. I have already calculated the values and would like it to look something like this:

enter image description here

my code for the plot is:

corn_germ$Treatment <- factor(corn_germ$Treatment, levels= c("UTC", "B/G/G", "B/GCa/GCa", "GCa/G/G", "GCa/GCa/GCa"))
corn_germ$Day <- factor(corn_germ$Day, levels = c ("4", "5", "6", "7"), labels = c("4 DAG", "5 DAG", "6 DAG", "7 DAG"))

corn1 <- ggplot(corn_germ, aes(x=Treatment, y=PercentGermination, fill = Treatment)) + 
  geom_bar(stat= "identity",position = position_dodge(), width = 1, colour= "black", show.legend = FALSE) + 
  theme_classic() + 
  theme(axis.title.x = element_blank(),axis.title.y = element_text(color="black", size=16, margin = margin(r = 10)))

corn2 <- corn1 +
  facet_grid(~Day, switch = "x", scales = "free_x", space = "free_x") +
  theme(panel.spacing.x = unit(0, "pt"),
        strip.background = element_blank(),
        strip.placement = "outside", strip.text.x = element_text(size = 14,)) +
        scale_x_discrete(expand=expand_scale(add=1))

corn2 <- corn2 + scale_y_continuous(breaks= pretty_breaks(), expand = c(0, 0), limits=c(0, 1.2), labels = scales::percent())+
  labs(x ="Day", y = "Percent Germination")

corn3 <- corn2 + rotate_x_text(angle = 90) +
  theme(strip.text.x = element_text(margin = unit(rep(10, 4), "pt")), axis.text = element_text(size = 12))

my data looks like this:

  Treatment   Day      `Percent Germination`
    <fct>       <fct>                 <dbl>
 1 B/G/G       4 DAG                     1
 2 B/G/G       5 DAG                    10
 3 B/G/G       6 DAG                    10
 4 B/G/G       7 DAG                    10
 5 B/GCa/GCa   4 DAG                     3
 6 B/GCa/GCa   5 DAG                     9
 7 B/GCa/GCa   6 DAG                     9
 8 B/GCa/GCa   7 DAG                     9
 9 GCa/G/G     4 DAG                     2
10 GCa/G/G     5 DAG                    10
11 GCa/G/G     6 DAG                    10
12 GCa/G/G     7 DAG                    10
13 GCa/GCa/GCa 4 DAG                     2
14 GCa/GCa/GCa 5 DAG                     7
15 GCa/GCa/GCa 6 DAG                     7
16 GCa/GCa/GCa 7 DAG                    10
17 UTC         4 DAG                     2
18 UTC         5 DAG                     8
19 UTC         6 DAG                     8
20 UTC         7 DAG                     8

Other questions asked seem to be looking for adding count labels, but each one of my bars only has one count which seems to be why mine isn't working.