Fixind Defender suggested security issues slowed down my site?

Hello,
I chose category "General Wordpress" for this issue since it is actually not defender's "fault" if this happened but I found it is generally suggested to do the security improvements that Defender suggests doing. The Defender just makes complying them much simplier.

Attached is the screenshot of all Defender recommended security improvements I made yesterday.

The side effect of it (on my guess) is though a very slow website.

Yesterday morning I tested speed of two of the test pages of my website under construction.

This page gave me 92 points on desktop speed by google site speed test which is great!

This page gave me 78 points on desktop which is also ok.

I don't remember the mobile speeds but they were moderate.

Then after that I went to improve the security of the website by correcting all the issues stated by Defender as recommended to improve.

You can see the Defender suggestions attached to this post.

I tested using the site after applying these improvements and everything seemed to work fine and I was really hapy. At first...

Until I went to run another speedest with the google site speed test

The speed is now 60 on desktop and 51 on mobile as you can see.

Even more downgrade was on the another page's score which dropped
from 92 in desktop to 55 on desktop.

This is a really devastating drop at speed!

The speed test says the issue is with slow responding server.
I did not have this problem before.

Once again I am not "blaming" Defender for this since
it is commonly suggested to do the security improvements
that Defender recommends doing.

But my questions are:
1. Is this reducing of speed caused by the security improvements I made?
(my quess is yes because I didn't do any other changes to the website yesterday)
2. If the speed reduction is due to the security improvements then what can
I do to get my website speed to where it used to be?