why are my lower leaves yellowing?

the lower leaves on my plant about 3 or 4 weeks into flowering have started yellowing and the sucker leaves have started to curl. i dont know why this is happening and the growth has stomwhat slowed down.

anyone ever read the self-help threads?

anyways... i can only guess that there is/was nutrient lockout for some reason. the plant looks small enough (and the container large enough) that there wouldn't be a lack of available nutrients. look at pH being off. or overwatering. or compacted soil conditions. if none of these things are a problem then a 20-20-20 ish fertilizer should correct what appears to be a Phosphorous deficiency ?

(EDIT) just noticed most of the lower leaves are also curling down... that would be another symptom, besides yellowing, to take into consideration.

i read the self help but alot of the symptoms seem to overlap possible reasons.. the top leaves are starting to curl somewhat too and some small brown specks are starting to appear