Slow growth from root-bound plants?*Pics*

[GigZ-16]

I have eight plants under fluoro tubes in a stealth closet grow room. They were put under 12/12 a week ago and I'm not sure if their presently slow growth is do to a root bound issue or to my plants readying to flower and bud. There my first plants I've grown enough to flower. I don't know if the atmosphere is even relevant in my question but I'll throw it in there.

age: 28 days
flowering stage: 1 week into
Lights: Fluoro Tubes
Soil: MG seed starter with no time-release nutes
temp: 75 degrees daytime, 70 degrees nighttime
humidity: presently averaging 50%
PH: tester has dead batteries
Nutes: no nutes after a nute burn 2 weeks ago with a full recovery

Also: I have had a recent infestation of some sort of bug that eats holes in leaves. I've been misting with a soap and water spray and the infestation has been vastly reduced.
And I have a fan blowing on the plants.

I have a blurry picture in my profile (I don't know how to upload a pic into my threads.) and it shows the size of the plant compared to its container.

Is the slow growth from flowering stage beginning or from root-bound?

[FrostAie]

From your pictures I couldnt see the full size of the pot but I usually start my babies in 32 ounce plastic cups and then move them to a at least 3 gallon pot. IF there is holes on the bottom look for white roots

[GigZ-16]

I don't have any holes for drainage. But I can see roots coming down throughout the sides of the cups.