Freshly painted skirting board turned yellow

[secretfreckle]

Last weekend I sanded down our bannisters and hall/stairs skirting boards, painted with Crown aquaflow undercoat and then yesterday, with Crown aquaflow high gloss paint in white. Today it is all looking yellow. What can I do??

Did you use primer?

Some kind of stain has leaked through. (previous paint, particularly that awful trend for stained wood etc can leak through). You basically need to "block" it.
Zinsser BIN is a great stain blocker, always use it on anything coloured

I found this with Crown white gloss a few years ago and haven't used it since. I use Johnstones which doesn't yellow.