Rhopalurus garridoi are a joy to own.....Good eaters, fast growers, animated and if you keep them out of direct light, very day showy. Although, there's no need to keep them on such a damp substrate.....R. garridoi are found in the desert like coastal regions of southern Cuba so a dry substrate with misting and/or water bowl is the way i keep mine...together with plenty of vertical climbing surfaces.
I've never had any of mine get mycosis but i don't keep them on a damp substrate.....i'm not sure if they are especially prone to it though.
I've had mine for a couple of generations now and i'm getting quite good at sexing them at lower instars based simply on their overall form. To my eyes your 4i looks female and with these guys moulting out to adult at 6i that'll make her semi sub adult