push button code - missing purpose

Hi everyone,

I'm attaching a picture of my breadboard. Also, when I open the serial monitor, I immediately get the following:

2 State changed 1

5 State changed 1

8 State changed 1

9 State changed 1

10 State changed 1

14 State changed 1

15 State changed 1

16 State changed 1

17 State changed 1

18 State changed 1

and then start pushing buttons one by one from bottom to top one by one, I get the following:

2 State changed 1

5 State changed 1

8 State changed 1

9 State changed 1

10 State changed 1

14 State changed 1

15 State changed 1

16 State changed 1

17 State changed 1

18 State changed 1

10 State changed 0
10 counter: 1
10 State changed 1

14 State changed 0
14 counter: 1
14 State changed 1

15 State changed 0
15 counter: 1
15 State changed 1

16 State changed 0
16 counter: 1
16 State changed 1

17 State changed 0
17 counter: 1
17 State changed 1

18 State changed 0
18 counter: 1
18 State changed 1

From what I can observe while I'm pushing the buttons, the first 4 buttons (at the bottom) give no response.

Thanks so much for your responses!