My guess is that you are probably using more strings in legend(); e.g: you are plotting only one array and passing two legend strings like below
plot(x,y);
legend('labels', 'label2');
you could probably do
h= figure();
plot(x,y)
hold on
plot(x, y2);
legend('labels', 'label2');
You could as well do something like this for each of your plots
h= figure();
hold on
plot(x,y);
legendmat = [legendmat; 'label1']
legend(legendmat)
% some other code
figure(h)
plot(x, y2);
legendmat = [legendmat; 'label2']
legend(legendmat)
% some other code
figure(h)
plot(x, y3);
legendmat = [legendmat; 'label3']
legend(legendmat)
