Issues with MacOS running slow

Hi guys, new to Reddit and this forum so please bare with, basically I have a late 2014 Mac mini (i5, 8GB RAM) and I used open core to install sequoia and it was running great after I put my SSD in there. But the issue I had was after 2 weeks of use, it became really slow to open apps page or just open apps or finder etc and my whole dock turned dark (as seen in image below).

Reinstalled from usb again and worked like butter. Another couple weeks and it did the same. So I thought I’d downgrade to sonoma and it was working fine. Now it’s done the same thing again and it’s just really slow using the system. All I do on there is watch YouTube and Netflix nothing too taxing only have a tab or two open and just the browser open really. Any thoughts?

Thank you