New Grower that needs some guidance. Purple stems,bugs,yellowing and burnt tips.

Hey everyone, I am new to the group and would greatly appreciate some advice.
I have two plants about 2 months old, 1 is (what i was told) purple girlfriend, the other is Grand daddy diesel. The rest are seedlings from seeds i found in some trim. Im using cfls in a 3x3x3 box i made. Temps stay around 75-80 and humidity is normal. I havent given any nutriens as i wouldnt know what im doing.My first problem is my plants have some kind of bugs that leave a slimy looking, white-ish spots on the leaves and little black spots (im guessing bug poop from what ive read). Howcan i get rid of them. Next is the yellowing on the lower leaves (about a week old problem). On top of that all the tips of the leaves are turning brown on both grown plants(not the seedlings) and the stems are turning purple fast. Please help, any will be very much appreciated. Check out the pics for reference.

2 months old and no food you are starving the ladies. What kind of soil are you using?

i got same problem..but urs look great compaired to mine..mine went to crap in a few days after transplanting..im sure the purple is the plant gettn cold..mine went from a nice warm closet to a 70 degree basement and they turned color..
but im lookin for the same answers with the other questions..im new to using dirt..so thats where my problems starts..and using Miricle grow..good luck..im just a thread above ya here askn the same thing..a few guys answerd if that helps ya any..

If using Miracle Grow don't add nutes cause you will just burn ya ladies. MG has time releasing nutes that release every time you water. But IMO if in MG I would transplant them out and put them in some organic soil that you can get from lowes mine was $7 for 12 gallons. Then buy some organic nutes too from the same place and start ya girls on that. But overall ya girls are not that bad. Also what kind of water are you using tap or RO?

I have no idea what kind of soil it is, I got them from a friend of a friend.