Yellow leave spot(septoria) ?

[Youngnobleoutlaw]

I have 4 blueberry indica clones . They are growing in bat mix .I am feeding them on canna nutrients a+b, pk13/14 and canna boost once a week . I give them water inbetween ph 6.5 .
I am using a marshydro sp3000 about 22 inches above canopy.
My grow room is 3x5ft. I have a 4inch exhaust fan and a 16inch ocsilating fan. The temps are 25 during lights on and between 17 and 19 during lights off. Humidity 55 to 65 ..
They in the 4th week of flower . I have checked the ph on the run off after watering and it' comes back at 6.5.
I have give them calmag once a week since watering (0.5ml per liter)
This week they have developed tiny brown spots on the fan leaves. The spots are more to the tips of the fan leaves and some leaves are going yellow . All the 4 plants have the same problem.
I have been trying to find out if it's yellow leave septoria or calmag deficiency.
if it is septoria can I use anything to stop the spread which wont hurt the buds .

Thanks in advance

[MeEasy]

I'm thinking you might have three things cal-mag deficiency and possibly some bugs. I would look very closely under the leaves with a magnifier of some kind. Some of the spots are different more round and that's what makes me think bugs. Check out this link it has some good info about plant problems and a problem flowchart I found if you go through the yes no questions and follow the map it's right on with your problems

https://www.growweedeasy.com/5-step-solution-to-most-cannabis-growing-problems