i dont see any obvious nute-burn. what you do have is a deficiency of some sort. what soil are you using? have you administered any other nutrients other than bio-bloom? a three week old plant should not be lacking in much unless there are no/ or very little nutrients in the soil. this is a guide that may help you a bit
Yellowing of Younger leaves............. Fe, Mn.
Yellowing of Middle leaves................ Mo.
Yellowing of Older leaves................. N, K, Mg, Zn.
Yellowing Between veins................. Mg, Mn.
Old leaves drop................................ N.
Leaf Curl Over.................................. Mg.
Leaf Curl Under................................ K, Cu, Over Fert.
Leaf tips burn, Younger leaves........ B.
Leaf tips burn, Older leaves............. N, Zn.
Young leaves wrinkle and curl.......... K, Zn, B, Mo.
Dead areas in the leaves................. K, Mg, Fe, Zn, Mn.
Leaf growth stunted........................ N, P.
Dark green/purplish leaves and stems......... P.
Pale green leaf color..................................... N, Mo.
Leaf Spotting.......................................... ...... Zn.
Spindly........................................... ............... N.
Soft stems............................................. ....... N, K.
Hard/brittle stems........................................ P, K.
Growing tips die........................................... K.
Stunted root growth.................................... P.
Wilting........................................... ............... Cu.
Use this chart as a reference ONLY. This is not a guaranteed diagnosis of your plant and you should only use this as a guideline to help you figure out what your nutrient solution is lacking...
try this if thats confusing ---
http://www.marijuanapassion.com/forum/attachment.php?attachmentid=158412&d=1295751999