Pick those leaves of asap! Any leaves more than 50% damaged/burned should be cut off so that they don't use any nutrients other healthy leaves could be using.
your plants also need a humidity of 60 to 70% to grow efficiently. Circulation is SOOOOOO important. I have two small oscillating fans, an inline fan and a regular box fan in my 8x10x3 ft closet and its not enough at times. Your plants are probably deprived of CO2 as well.
As a grower, I must say...
Your plants need to be in 3 gallon (or more) pots ASAP!
Then water them with appropriate nutrients. It looks like they are not getting enough nutrients because the soil around them cannot hold enough. Transplant them asap, lightly mist the underside of the leaves...
Hazee,
What kind of light are you using? How close is it to your plant? It look like it could be a light problem (assuming you are giving it nutrients with sufficient nitrogen).
I don't think its a nitrogen problem because your stems are not red.
I am growing 6 plants and they are all...
Trust me, if you are not getting 16-18 or more hours of light your plant is not going to be very big nor is your yield going to be very high. Consider setting up an indoor garden if you have an extra $2000 and some time.
-K
It looks like a phosphorus deficiency.
A lack of phosphorous causes stunted growth and smaller leaves; leaves turn bluish green and blotches often appear. Stems, leaf stems, and main veins turn reddish purple starting on the leaf's underside.
The leaf tips of older leaves turn dark and...