Is this mould caused by a leak?

[fairgame84]

I've noticed the skirting board behind the toilet has split and gone mouldy recently.
I'm in a rented house and have been here 7 years. No other mould issues or anything. Obviously I need to let my LL know but do you think this is a leak or something that I've done/not done?

The first pic looks like either a leak or condensation dripping. Second possibly a leak.

These type of things are usually just something a homeowner would keep on top of so not really anything you've done.

Is it soft and spongy?

Just zoomed in, yes landlord should sort that.