Recoding turns everything into the same value in R

I'm practicing R and I created a new column that had continuous numbers in them called ROI, and wanted to recode the number values into string values in R like this:

df = mutate(diabetes_df, ROI = ifelse(ROI < 18.5, 'Under', ROI))
df = mutate(diabetes_df, ROI = ifelse(ROI >= 18.5 & ROI <= 25, 'average', ROI))

diabetes_df = mutate(diabetes_df, ROI = ifelse(ROI > 25 & BMI <= 30, 'above average', ROI))

This works normally and it displays these words wherever the condition is met, however when i put the last ifelse statement :

df = mutate(diabetes_df, ROI = ifelse(ROI > 30, 'OVER', ROI))

It turns every value in the new column I made into the OVER value. I was wondering if anyone knew how to make it so that it would only say OVER for where the condition is met?