A (1,lambda) ES with individual step sizes

I'm trying to find a good solution with an evolution strategy for a 30 dimensional minimization problem. Now I have developed with success a simple (1,1) ES and also a self-adaptive (1,lambda)ES with one step size.

The next step is to create a (1,lambda) ES with individual stepsizes per dimension. The problem is that my matlab code doesn't work yet. I'm testing on the sphere objective function

function f = sphere(x)
    f = sum(x.^2);
 end

The plotted results of the ES with one step size vs. the one with individual stepsizes:

The blue line is the performance of the ES with individual step sizes and the red one is for the ES with one step size.

The code for the (1,lambda) ES with multiple stepsizes

% Strategy parameters
tau = 1 / sqrt(2 * sqrt(N));
tau_prime = 1 / sqrt(2 * N);
lambda = 10;

% Initialize
xp = (ub - lb) .* rand(N, 1) + lb;
sigmap = (ub - lb) / (3 * sqrt(N));
fp = feval(fitnessfct, xp');
evalcount = 1;

% Evolution cycle
while evalcount <= stopeval

    % Generate offsprings and evaluate
    for i = 1 : lambda
        rand_scalar = randn();

        for j = 1 : N
            Osigma(j,i) = sigmap(j) .* exp(tau_prime * rand_scalar + tau * randn());
        end

        O(:,i) = xp + Osigma(:,i) .* rand(N,1);
        fo(i) = feval(fitnessfct, O(:,i)');
    end

evalcount = evalcount + lambda;

% Select best
[~, sortindex] = sort(fo);
xp = O(:,sortindex(1));
fp = fo(sortindex(1));
sigmap = Osigma(:,sortindex(1));

end

does anybody see the problem? Thanks