Fish flour

I use botanicare pro bloom, sweet and karma and am in my 5th week of flowering.
I have yellowing on 3 plants, couple older leaves and now some yellowing new growth around the bud area.

My ph was in between 5.8 to 6.4 and now i brought it down to 5.5 and will try to keep it there.

I am pretty sure it is a zinc problem, so i went to store and the guy give me fish flour and i also got microblast.

I am using 2 tsp. per gallon on 6in. rock-wool cubes with my ebb and flood system. and i am putting it directly on the cubes...

I also sprayed microblast on the leaves..

My question is, Is this OK being that it is in my 5th week of flowering????

Thanks...

Its normal for the lower leaves to turn yellow. Most fertilizers have all the micro nutes in it. I would think that its a nitrogen def which is normal.

Yea, That is what i thought at first,but the fish flour did not work, so i used microblast for the zinc... I will soon see....

Thanks