when changing coolant brands it is VERY important to clean extremely thoroughly with bactericide.
I wasn't really having problems with my coolant but supply chain was bad so I switched brands.
Machines stank so bad in 1 week that I was retching just walking by them. I was pissy with the rep that sold me the new "super" coolant. I had major work stripping and cleaning with their special bactericide and of course dumped all my tanks.
Turns out that if I would have run the bactericide in the old coolant for a week FIRST (doing lots of machine hose downs) it theoretically would never have happened (so I am told).
Now I have aeration on timers and can go a month between uses without it getting bad.