1 month into my first grow...help!

Hello everyone!
I have been having some struggles with my ladies lately. I have three previous threads on them where I adjusted the PH and watering schedule. I am using FFOF soil without 25% perlite because I had found that out after I had planted them. The top dressing of new FFOF now has 25% perlite and a feeding/watering schedule of just RO water and one tbsp of molasses per gallon at a ph of 6.5. I also added a exhale CO2 bag last week when they had seemed to recover. One has recently developed what I thought was black is now purple tips and veins also very droopy; with a slower growth rate. And the other is also droopy and canoeing. I was wondering if anyone knew what this could be! I would love to get them back being happy! I also have two more lights I have been waiting to use and am wondering when they need more light than the current 600w mars hydro.
Thank you so much for all the help!

Temp maybe? They are young tho too so maybe just adjusting.

I was thinking the same thing? Is it getting cold cold at night?

I live in CA so the lowest the tent has seen is 65 degrees at night usually around 70 at night. I usually try to keep it around 75 during the daytime with the hottest being 84. If the plants change temperature by about 20 degrees would that possibly shock them? Thank you!