I’m in the 3rd week of flowering in my first grow, can you please help me find out what is causing these dark spots on her leaves.

Lots more information is needed. Read this post so you know what to include:

https://www.mrgrowit.com/forum/grow-community/read-me-first

Hi, More information would be helpful.

What have you been feeding them and what kind of soil are using? Do you know your PH and PPM?

Not sure about the brown spots, but the leaf tips look like you might have nutrient burn.