C99 and Blueberry strains

Pics 1&2 are C99 #1.... 2&3. are C99 #2... and 3&4 is blueberry. getting this yellowing that's had me a bit puzzled. looks like Nitrogen difficiency, but this late into flower??? 90% sure it's not cal/mag problem. Bumped up the nutes thinking possible nute difficiency since I wen about a minth into flower without needing to add any nutes to looks like I need them. At any rate... I'm keeping my eye in her. at this stage I cant afford to loose too much time tryi g to figure out what's happening. any suggestions from anyone who has grown canuk's bluberry???