nute bud burn?help!

hello.just made a user acount here.so in this case ill just say greetings.i am growing my 3rd crop and this time the biggest ever.i have some issues with blueberry from dutch passion seeds and leda uno from kc brains.also same problems with skywalker .i will upload photos of close ups of buds.i would be more than gratefull to read you opinion.did i over/under fed the plants?not enough fresh air ?root rot?it could be just harvest time that comes?too much heath?i can tell you that i use 6x400w hps +4x250w hps (each in between the 400w lamps) i have a tnumber of 52 plants in 16 square meters room.proper venilation and all.the meal that i ofer them never passes 0.80 -0.82 E.C and the ph at 6-6.20 allways.the inside room temp is at about 23 C' in the mornings growing til 28C' after 12 hrs of light(in my region it is still summer)i have the humiditty from 50% up to 70% sometimes a day after i water.what am i missing?i want to put up one last thing with the blue berry.2 of the 4 tops got lamp burned in the 2nd week of flowering.got burned because i probably veg'd it to long and it overgrew in height.because i had an unsupervised fan somewhere to high it pushed the plant towards the lamp and itgot severe burns and recovered hard after this.the lowe part still produces tho.here i need your help to tell me from the pics whathadeal



 
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