Harddrive and SSD disappearing in My PC

Hey all,

I have a Windows PC with 3 drives in it. A 250GB SSD and 3TB HDD that came installed and a 1TB SSD I installed myself a couple years ago. Recently I've been having issues where my HDD and the 1TB SSD frequently vanish from the My PC window in File Explorer.

I've tried a few things: restarting my computer, opening up my PC and unplugging/plugging in the cords leading to the drives in question, defragmenting/optimizing the drives when they do reappear.

I'd be questioning a drive issue if it was just one having issues, but two drives starting to have issues around the exact same time seems weird to me. The main cable bundle (yellow, red, black wires) coming from the mother board is plugged into a splitter that then plugs into each of those drives. I'm wondering if perhaps its something wrong with this splitter? Sometimes one drive will reappear (usually the HDD first) then the SSD.

When I go into 'Optimize Drives' I can see the ones it recognizes (the 250GB SSD is always present and this is what my operating system runs on), and then any drives that are not appearing in My PC show up as 'unrecognized' here.

Apologies in advance for my poor terminology as I'm not a tech expert by any means. If anyone has any idea what I should do next I'd appreciate the help!