You have to open them individually:
fid1 = fopen('testfile1.txt', 'wt');
. . .
fid5 = fopen('testfile5.txt', 'wt');
WRITE TO FILES, THEN CLOSE THEM
fclose(fid1);
. . .
fclose(fid5);
or if you don’t have any other files open that you want to keep open, you can use:
fclose('all');
