Why there is 4790k and H100i gradual raise in temperature by 20degree in 10 months?

[Foxeye]

I just noticed my h100i and 4790K hitting 95 on corsair Link and 105 max on a core in HW monitor. I don't understand why this is happening checked the same months back during summer thought it happened because of the ambient temperature. But now its chill in here the room temp @36 normally.
When i built my PC the temp was 85 Max on a core in HW monitor.
I recently cleaned my PC (roughly removed the naked dust) is it because of that ? Or may have the thermal compound lost its property ? In 10 months ?

 

[Varun1801]

Maybe you forgot to clean out the radiator? It could be thermal compound, but, as you said, 10 months seems rather short

 

[William Henrickson]

Yeah, you might have had too thick of a paste and it dry cracked like desert mud.