Not sure whats going on with one plant.

So I started with 4 plants 2 were xed out one male the other in a horrific accident. So I have two beautiful females left. I am using MG soil, 6 23 watt cfls, Just water no nutes. I am 4 weeks into flowering and one of my ladies is a wild one and taking off with pretty decent buds. My second lady was doing superb all through the veg peroid has seemed to just slow down almost to a complete halt. She has had some stress put on her and I could understand maybe she is playing some catch up because I am slowy starting to notice a lot of calixa's, but no where near as much as my first plant which has beautiful buds. The one place I am not seeing anything at all is at the very top of the plant though? Could it just be that the lady is she and going to take just a little bit longer to fully bud? Or is it something else? By the way I am growing WW if that also helps.