I am in the process of creating my sour-dough starter.

I've been mixing in water and "strong bread flour" around a 1:1 ratio (100g of each, slightly more water to make the mixture wetter).

The mixture sits on the side between feeds (approximately every 24-36hrs), and has bubbled up, as can be seen on the side of its home (a cleaned out old 1ltr ice cream tub).

However in the last couple of days, I've noticed a distinct vinegar smell coming from it, and it seems to slightly separate: brown-ish water layer and a thick dough layer.

Do I need to worry? I could have contaminated it, as the kitchen is always all over the place. And the feeds are supposed to be every 24hrs or more often according to online sources, so I may not have fed it often enough.

I'm in the UK, so 15-20C in the kitchen.

TL:DR - vinegar smell from sour dough, is that a problem?