yeah they do look small for 4 months, first wat sorta seeds did you use, bagseed? and did ya germinate them properly? The root is definitly stunted maybe a calcium deficiency, i dont really know about the purple leaves, what do the purple ones feel like? If there britle you need some phosphorus up in there. have ya got any close ups of the plant budding? all in all lad you should be happy your first grow turned out to be female and its starting to flower, dont harvest your bud to early,still looks like you might get some good bud off it