Hmmm .... I dunno Bro.
Can you be more specific than "plant light"? Is it actually watts or equivalent to? What is the light temp (Kelvin = K)?
As a rule you want at least 100 watt min per plant. You want 6400/6500 K for veg and 2700 K for flower. Also it looks
like the light could be closer. Depending on how hot it is. If your hand is comfortable under the light then That is distance
you can move the light to. Closer the better.
The plastic bag thing .... Not gonna work. Your gonna hermie your plant by messing with the light periods and that is
NO WAY light proof. Use some cardboard and do a much better job on that. You will want a good air flow also.
I've used plastic totes for a stealth grow. You can stack two or three on top of each other. Then cut out the bottoms
to make one tall chamber. I've used up to a 400 watt HPS in one w/ good ventilation.