Problems with Saxifraga stolonifera

Hi. I have a problem with my Saxifraga stolonifera. I got the plant in June and it has been fine until a few weeks ago. It lost its colour and has these pale spots on some of the leaves and a few of the leaves are dying. I don't think that this is an under/overwatering problem. It has a springtail infestation but I have read that springtails do not kill plants. It is in bright indirect light and all of the new hanging growth is healthy looking. Doed anyone have a guess at what is harming my plant? Thanks!

 

Perhaps it needs feeding or a change of compost if that's what it's planted in. Nutrients disappear from compost after approximately six weeks.