blueberry keeps burning at 10 mill, why???

i got some blueberry that burns if i give them 10 or more mill (PER 5 Gallons!)of organic fert.(botanicare). they are starting their 4th week of veg and lookin like they need a lil more nitrogen in their diet. i have been foiliar feeding to keep them growing. if i didnt who knows what would happen. they prolly would not make it this far.im afaid that when they bloom imma run into major deficiencies because foliar spraying isnt good for buds. i have had other strains that at this point in veg would be getting 30 - 35 mill per five gallons. is this typical for blueberry or are my roots weak?

promix
botanicare at 10 mill per 5 gallons.barely nothin
ph @ 6.4
4 weeks of veg

just get a bag of nitrogen, feed less n add extra nitrogen if tats wut you think it is... walmart sells bags of it, like 20-0-0 r some shit

fair enuff. the problem is i dont think i can get enuff nutes to the roots without them burnin up(indicated by tips of leaves turned brown after watering). as of now while inm in veg i supply extra nutes to the plant through foliar feeding, however, when in bloom foliar feeding is not a option due to nasty tastin buds and risk of growing mold on them. so what happens when i get a phosphorus def, in bloom. it would almost be impossible to correct cause my plants wont accept more nutes at the roots cause they burn too easily.whats up wit my roots?is it the strain???????????????

Remember, some strains are VERY sensitive to nutes. Pics?