After my last trackday in 2018 the pedal felt softer. I thought it was the fluid that was cooked but did not change it as it was already late in the fall.
It turns out it was a leaking caliper piston seal and during the winter all the fluid leaked out and made a mess of everything it touched:

The piston fell out during disassembly but looked ok.

I was ready to bin the whole kit and go back to stock. Not overly impressed by the performance.
But the seals and even complete set of pistons was readily available on their website. The seals only was cheap so I'll give it another go.  Also ordered some new pads that might be a tad more agressive (hope).

The pads that came with the kit was not worn out, but the brake fluid had leak had soaked the inner pad making it useless.

I haven't put any strain on them yet but the leak is all gone. Roumours says it's possible to use higher quality seals from AP or some other high end brand. If more seals fails I have to look into that.