I cannot see, how your code would show the described behavior (assuming that, you have connected the buttons correctly with a pulldown resistor). But your code can be greatly simplified, which would make it less error prone.
You have 8 buttons, which screams for the usage of arrays (IMO you should always use arrays, if you have more than 2 or 3 equal ...
So based on the information you provided I understand that the issue is that both the if(switch1state==HIGH) and the `if(switch2state==HIGH)' statements evaluate to true if either switch is flipped. That means one of the following things is happening:
1) Somewhere in your code you're mixing their values and assigning ones value to the other
2) Your ...
It turns out the problem was the A2 pin on the board.
When I used the A0 pin (or a different board) the problem goes away.
I realised something was wrong when I noticed the values from the pot were strange (I expected values in the range 0 - 1023, but was receiving values from 170-250 ish).
The String+ operator is very expensive. High likely what it does is:
Create a new block of memory to accommodate the old string content and the to-be-concatenated text.
Copy the current String to a new string location
Concatenate the string
Free the old memory
Besides creating memory gaps which can be disastrous for the just 2 KB SRAM of the Arduino Uno, ...