Scum layer on barrel aged brew

[Trifixion]

Hey everyone, needs some opinions on this. Been barrel aging my brew for several months. Checked it 3 weeks ago, everything was spot on and no problems. Just gone to take a sample today and I’ve got a layer of white scum in the surface. Took a sample, tastes fine, smells fine. No souring or off tastes. Could this just be floating yeast situation or is it wild yeast infection that hasn’t go beyond surface level yet ? I’m gonna rack the entire lot off and add campden tablets and finings and see where we go from there