iv grown from seed to chop with 2 135 watt LED UFOs(40 3watt LED chips per UFO) they were sufficient for 1 single plant through flower and no where near equivelent to even a 400watt HPS, although they did do the job for one plant, i only yielded 1.3 oz off that plant but i was also using some no name brand crappy soil and was over feeding with Fox Farms trio of liquid nutes which in turn game me lock out issues, i think i may bust out the LEDs here in the winter and ill see what i can do with good soil and nutes, but as everyone else has said, upgrade to better lights, grow out 1 plant if you want but that LED fixture you have aint gonna cut it for 4 plants, just no way. so id get a 600watt HPS (min wattage id recommend for that area), also as 7thg said a better REAL exhaust fan and yes suck the air OUT while letting the fresh air get pulled in through passive vents, this creates negative pressure which will cut down on smells leaking out, the current set up of pushing air INTO the space is just going to blow stink out of any little crack it can and your going to smell it more then if it was negative pressure since all the smell is comming out of one place, the exhaust fan... id say at least get the 600 watt HPS for flowering, the LEDs will actually work very well for vegging the plants, assuming you get more fixtures for 4 plants, i personaly dedicate 1 135watt UFO per vegging plant untill they are larger then 2 UFOs... but hey thats just from my experience with both T5/HPS and LEDs.
so to sum up, yes LEDs do work from seed to finish, need multiple per plant or a bunch of fixtures for multiple plants. also UPGRADEs are highly recommended.
