Is it Nutrients burn or nutes lock up or something else?

White widow, planted on June 28th but by that time i didn't have a Carbon filter system, Until july 21st I installed one and realized the plant were stunted like hell, for the first 3 weeks of its life. it was so tiny and i barely notice a growth not until i installed the carbon filter i was so shocked with the difference of growth, but then i got confused with the feeding schedule, What should i treat the plant like, a seedling? or a plant in its early stage of vegetating, Anyway let me get straight to my question, its in a 1 Gallon reservoir of Aerogarden system and the last water/nutes mix was on August 2nd, 4 days ago... I added 1.3mL of each micro,grow,bloom from the flora series nutrients then checked the EC, it wasn't higher than the previous nutes mix, so i added another .4mL again then i added Rhizotonic, Been using it for a month now it helped the plant to survive and grow a bit in the time when i didn't have the carbon filter, anyway the plant seemed to me liking the nutes, I check the EC everyday and it went down from .79 on the day when i mixed the nutes to .53 but the leaves have those brown spots looks like a nutes burn and i'm confused now, because i doubt the dosage of nutes is high plus the EC is going down everyday...

i make sure the PH doesn't go higher than 6.3, every time i add PH down to have it on 5.7-5.8 after like 12hrs or so it goes up to 6.2-6.3 sometimes higher but i try my best to not add those chemicals (ph down/ph up) everyday to the reservoir to avoid ph fluctuating shock
I add ice cubes everyday to have the water temperature in the reservoir to 19C, and after like 12-16hrs the temperature raise to 22-22.5C

Room temp. 23-24C at light on time 17-18C when the lights goes off

here's some pictures of the plant i took today and i would appreciate anyway can simplify the confusing of the feeding schedule i have now due to the stunting problem i faced for like 3 weeks from not having a carbon filter and what should i treat the plant like now and is my dosage of nutes are fine or what

I spray the plant with water mixed with neem, that shouldn't be a problem right? i started that few days ago

i think that isn't bugs

It could be bugs, not sure. Is the Neem helping? Any damage already done is permanent but if its mites the Neem Oil should be at least helping to control new spots, leaf yellowing, and damage from appearing. Sometimes you'll see webs too. If you can get a hold of a microscope or something that has 30x mag, look at the undersides of the leaves for bugs. I could see the egg clusters with a 10x mag glass once I knew what I was looking for, off-white fuzzy looking roundish globs on underside of leaf.