Hard Mode:Last puzzle opens water tanks

Hello big Fish Today is Tues. 6 Sept 11 at 5:53 pm in Germany.
Please help me solve the last puzzle. Your walkthru states; There are 4 red buttons to change symbols etc. Then your solution is as follows
AX2,B,A,C,AX2,B,C,X2,AX2,CX3. Your picture shows only the use of three buttons. A B C. Well I have tried for days to figure this out and I am at the point of bashing this computer to bits. What is the solution????? Have a nice day Alexandra