IN NEED OF URGENT HELP! Please give me good advice :)

Hey I am new to Cannabis growing, this is my first grow. I started with 3 seeds, all germinated, 2 became female, and 1 became male (thrown)

Light 600 LED (Amazon Cheap Light) (going to ramp up to 1200 LED very soon)
Nutrient given General Hydropnics
Soil and Warm Castings for medium
PH around 6.2~6.7 but didnt measure soil PH.

4/01 Seed germinated
6/18 - Today (Really want to transition to flower)

If you look at the pictures, one is really growing well without any problems.
The other plant has problems occuring and its getting worse. I thought it was Nitrogen Toxicity at first, Then Overwatering, Now I am thinking its Root Rot and Massive nutrient deficiencies. I dont know what is the problem and I cant send these to flower until I fix this issue. Can anyone Help me fix this issue with this plant showing signs of something but I dont know what it is. Also, there is these small white spots ( I dont think its powdery mildew but it might be), Having anxiety over these..
*I havent given any nutrition for past 7 days now.

Tell us more. What is your water and feed schedule like?

I water when I feel like its dry, 2-3 times per week or sometimes 2 times. For the feed, I've given a lesser amount. probably 1 week and 1 week off cycling like that.

I also thought that the plants are uptaking nutrients from the leaves because they need nutrients for top parts of the plant.

Can you give us some info on exactly what and how much you're feeding those plants?

“ Ramp “ as you said ….. up to better than amazon lights

Sunburn? How close is the light?

Even simple SF1000 QB style boards would crush any so called “ 1000watt led “. Which by the way is bullshit … your panel may say “600” but probably pulls less than a couple hundred watts if that.

HLG / Spider farmer / timbergrowlights / etc.

What is that medium

600W probably more like 50-80 true watts from that. The medium is just regular soil and warm castings mixture
I just saw some white small bugs in the soil, on the soil, I dont know if this is soil mites or spider mites cus they are not black but white..

Quickly seen on the plants the stems are red and the state of your leaves clearly indicates a problem of assimilation of nutrients due to a bad ph. add cal mag to your fertilizer mix at ph 5.9 your plant should assimilate its phosphate because cal mag helps in the absorption of phosphate and the cal mag absorbed to the maximum by the plant at 5.8 5.9 keep this ph in vegetation and 6.3 6.5 in flowering you should see a marked improvement.