Help me in solving KCLOSE problem

help
,
1

Can anyone explain me why this is failing for hidden cases

My code

# cook your dish here
# import math
for _ in range(int(input())):
    n, k = map(int, input().split())
    arr = list(map(int, input().split()))
    
    m = max(arr)

    if k == 1:
        print(0)
        continue
    
    for i in range(n):
        
        if m - arr[i] >= k:
            mul_fac = round((m-arr[i])/k)
            arr[i] += k * mul_fac

    mini, maxi = min(arr), max(arr)
    print(maxi-mini)

Problem Link: K-Closeness Practice Coding Problem - CodeChef