Dark shapes on leaves and yellowing tips (looks like some illness)

Hey! I have a problem with LowRyder#2. It is a very tiny soil grow - only 2 plants. The older one looks like this:

















What is that? ;/

nutrient lock up. I would flush. what kind of medium are youusing?

Nitrogen-based stuff ( N -5000 mg/l, K20 - 5000mg/l), but only 2 times and with 50% of suggested dose.

How much water (for flush) should i use for 4 liter pot?

err... you got a phosphorous deficiency.

if so, shouldn't leaves be dark? they go yellow.

Temps? Peace

http://www.onlinepot.org/grow/diagnosingplantgrowingproblems.htm hope this helps