What's the weird thing going on with page loading speed?

Question

PHP

I am developing a site and as it develops, the download speed decreases, it is clear more files more code everything is logical.
Now the average load in chrome is about 1.5 sec.
However, I have a second chrome that is almost identical, maybe 2/3 of the version younger.
And when I decided to test the speed there, the download speed was 5 times faster.
What's the matter?