Brown Spots?

hi there can i get bit ov advice my pistels on my cheese plants are starting to go brown 4 weeks in to flower and look like there burned but its not all over just odd few buds can u help please many thanks i use good vertilizer and i use canna boost spareing the for last 4 weeks ov flowering asince there in veg for first 4 weeks i fed it the dutd pro original bloomhydro/cokcs but i stopped using the dutchpro for the weekthey have ibeen in flower i just used the boost the i git told that i still need to feed the dutch pro bloom hydyo /cocos and thats my problem the pistels are looking like tnhey have bween burn but no ones near them so is the plant starting somety wrong i think its cos ive started useing the dutch pro and stoppingfor the veg then wen wen flower started ive just feed boost till now weeks in to flower and now​