Insects, disease or deficiency?

Hi there,

I'm 4 weeks into flower and my plant is showing some mixed symptoms.
As a novice grower I have difficulty distinguishing between these symptoms because many look so similar to each other.

I have found holes in leaves on lower parts of the plant, as well as brown areas on leaves and dried leaf tips.
I can't see any insects, but I can't explain the holes in the leaves.

I don't know if the browning & drying of the leaves is due to the environment being too dry or some sort of disease.

I feed my plant approximately once every 9 days, with 2 waterings every 3 days in between. I don't think I'm over or under feeding it but I may be wrong.

My lights are about 4 inches from the top of the plant, not much light reaches the bottom, so i added a couple to deliver light to lower parts of the plant.

Pics below, anyone have any ideas?

Info on grow:
Strain: Laos x Haze (Sativa)
Indoor, soil
6 20W 2700k CFLs & 2 fans (in-/out- let) (12-12 cycle)
GH Flora Nova fertilisers
1 CO2 bag
13 weeks old (from seed), 4 weeks into flower

If you could post a pic of the whole plant you would get more replies.

Looks like some kinda insects been at it

Hard to narrow it down with what I`ve seen try a layer of perlite or rock on top of your soil

Maybe spray with some kind of mild insecticide, its probably gnats or white fly or some kind of moth eating the leaf ?