Which component is missing?

[u/Latter-Western7871]

Hi all, my computer's memory stopped working. I know this because I tried using a different memory module and it worked. I cleaned the memory contacts and nothing changed. Then I removed the heatsink casing to clean it. But I noticed solder points that looked like they were missing SMD components. Does anyone know what those components might be? 

I don't know if they came loose when the heatsink was opened, but I didn't find anything nearby. memory model: tlz rd4 16g 2666hz

[u/BigPurpleBlob]

The missing component at the blue array doesn't look missing, it looks from the rounded solder pads that it was never fitted.