advice tips

Was curious to see if this is mold, and would like to know how to treat it. My dad went ahead and cut off most of the infected leaves without waiting for me to inquire about what the issue might possibly be first. So, id like to be able to help him out. Thanks for all the help in advance! :)...

1st timer here. Shoulda started it when I got the clone but it’s here now lol. Three week veg clone . Removed some of the big fan leaves. Advice, tips, thoughts and opinion are welcome. I’m here to learn 18hr schedule. Fed it for the second time and added a cal mag. In a 2x2 with exhaust fan...