I would stop using the Feser or any form of coolant immediately.
There is no need to rinse with alcohol. It doesn't dissolve minerals like water can.
Rinse your entire motherboard with distilled water and blow it off with compressed air. An easy job if you have an air compressor. Then let it dry overnight and it should be good to go.
Back on topic about the feser liquid. Any glycol solution is horrible. You might be temped by the misleading advertisement about being non conductive. It is non-conductive but your water blocks are usually made of metal and a tiny amount can get into the fluid and quickly make it conductive.
Back to why glycol solutions are bad. They dry very very slow. Once upon a time I was using feser one as well. Back when I was using it, I spilled some and I had to rinse and clean the motherboard, it was a pain. Worst of all even after a month I found drops of semi-liquid fluid on my case. A month to dry is unacceptable not to mention it stains plastics.
Use distilled water and UV reactive tubing. Coolant is a marketing scam much like Nvidia PhysX. Just to sell you something you think you need.
I actually had a leak a couple days ago. I didn't need to rinse anything since it was only distilled water. I just dried it with an air compressor with all the components in place and waiting an hour.