I imagine they are in need of replacement, if one had got so bad the air is leaking out and the tyre is showing fatigue damage. If it is a crack, it is definitely shot, no question about it.
To be honest I'm not surprised that someone has found this issue. When we see some of the rear inner wear pictures, it does indicate much more load is taken on the inner wall. Lower pressure will certainly make it worse, as it is like running partially flat, and using up the 'run on flat' properties.
BTW, is the inner edge showing the signs of inner wear, even if still OK at the moment?