Let’s talk about butter bleeds. This is when your icing has dried on your biscuit and the icing turns yellow.  This is more visible with white icing.
Why does this happen only sometimes.  It normally will happen when the biscuits are for a special occasion or for an order (and you have no time to redo them.)  I feel your pain.

Iced biscuits are more susceptible to butter bleeds during summer, especially if you live in a very hot climate.  What actually happens with a butter bleed is that the butter has melted in the biscuit and has seeped into the icing.
I have noticed I get butter bleeds when I do the following
1) I have got my timing wrong and over dried the icing in the dehydrator. If you do not use a dehydrator, you’ll find it was more than likely a very hot day.
2) My icing is too runny or too old.
3) My biscuits are too fresh when iced.

Ways to prevent butter bleeds 
1) Take note of what season you’re in and the temperature outside.  If it’s very hot, dry your icing (on your biscuit) under a fan or air-conditioned room to prevent the butter from melting and seeping into your icing.
2) Adjust your drying time in the dehydrator depending on the weather, increase the drying time slightly in winter and decrease the drying time slightly in summer
3) Use fresh icing and take note of the consistency, it must be flooding consistency not too runny.
4) Bake your biscuits the day before you ice them.
5) Lay your un-iced biscuits on roller towel (in an airtight container) to soak up excess butter. (This really helps)

There are so many theories out there and possibly other ways to prevent these dreaded butter bleeds.  I have simply shared my experiences and how I prevent this from happening to me.  I hope that it helps you in some way.

I sadly do not have images of any biscuits with butter bleeds.  I have definitely had them happen to my biscuits, when I do get another one (and I am sure I will), I will take a photo of it.
If you have never experienced a butter bleed, count yourself lucky.

Happy baking and biscuit making,

Ashleigh Temple