MacBook Pro slow speed issue?

Question

macbook

I have a 2012 MacBook Pro, version 10.8.5 with a 2.9 GHz Intel COre i7 process, 8 GB of memory and 1600 MHz.
Recently, the speed of the poppy has fallen very much - almost every time a program is launched, a rainbow appears.
The CPU is loaded with a maximum of 10-30% and there is still enough free memory. Recently I gave it up for repair (water in the keys and replacement of thermal paste), but they did not reveal any problems with the hardware, as well as checking the hard drive.

Answer 1

Maybe it's worth reinstalling the system on 10.10.4 and then put everything you need and it will work, I think it's better

Answer 2

try el capitan
really works faster