Sorry for only getting onto the bus now! Life has been hectic. But like so many others said, the crumb looks perfect actually. As you start to bake and the starter gets more established, the better results you will get. More active starter better bread. There is also a whole science behind feeding a starter to get optimal crumb structure. But for wholemeal or wholewheat that looks incredible! I can smell it through the screen. I find it that wholewheat is a bit more tangy, which is lovely. Was yours bit more sour?