Tall plants are they going to fill out

I've got five plants that have been in vegetative grow for three weeks now and I'm wondering if they will fill out more or if I'm doing something wrong right now they're under a t5 fluorescent light 6700 lumens on 24/0 I've tested for npk and all are at the right amOunt. I'm going to switch out the light today to a 400w mh light Pics are attachedD

Thanks for any feedback!
http://i1143.photobucket.com/albums/n640/unsightlyhair/Mobile Uploads/IMG_0170.jpg
http://i1143.photobucket.com/albums/n640/unsightlyhair/Mobile Uploads/IMG_1515.jpg

Seems like they have stretched majorly. T5's should be no more then 2inches above the top of the plant. Not much you can do now...

I've had the light 3in from tops of plants since they were clones but they still seem to be stretching.

Whats the wattage of each bulb?

Your plant looks like it is suffering from a lack of Potassium. This is caused by you not giving them a balanced feeding plan, or, it is caused by the nutrients being locked out due to incorrect ph of the water you are giving them. Get you ph under control before you do anything else or you'll just make the problem worse.

See this link for further diagnosis. https://www.icmag.com/modules/Tutorials/PlantTrouble/Merged.htm#Nitrogen

Potassium (K)
Potassium is involved in maintaining the water status of the plant and the
tugor pressure of it's cells and the opening and closing of the stomata. Potassium is required in the accumulation and translocation of carbohydrates. Lack of potassium will reduce yield and quality.
Potassium deficiency:
Older leaves are initially chlorotic but soon develop dark necrotic lesions
First apparent on the tips and margins of the leaves. Stem and branches may become weak and easily broken, the plant may also stretch. The plant will become susceptible to disease and toxicity. In addition to appearing to look like iron deficiency, the tips of the leaves curl and the edges burn and die.
Potassium - Too much sodium (Na) displaces K, causing a K deficiency. Sources of high salinity are: baking soda (sodium bicarbonate "pH-up"), too much manure, and the use of water-softening filters (which should not be used). If the problem is Na, flush the soil. K can get locked up from too much Ca or ammonium nitrogen, and possibly cold weather.

you need to regulate verticle growth. pinching the stems (not supercropping, just pinching) will focus the energy and increase lateral branching. maybe try some nitrozyme 5ml per GAL

from what i see in the pics there seems to be some discoloration in some of your leaves which would def be a nute issue... im also growing w/ fluorescent but im using cfl's not t5's and i can tell you first hand my lights have been within an inch if not touching the plants their entire grow... with fluorescents it is vey important to keep the light as close as possible... it might be worth it to flush but def recheck pH and nutes... you might also wanna consider topping or fimming them to help create a bushier plant... here is a pic of two of mine 5weeks of veg 1st day of flowering...

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I am very suprised at the lankiness for sure. i veg under t8s and have had great luck. these other huys must be on to something because going to MH wont necessarily help but it will be more expensive. hope you get it figured out, god luck