Yes air cooled hoods. It's funny when I went to my local hydro store to get new bulbs awhile back they said they dont carry them anymore because there prehistoric haha, as they try to sell me new lights and Sorry about that I should of said 4 part. So just dial back the A then. Maybe a stupid question but why the A and not the B?
I try to go to the hydro store as little as possible for that reason, they are like car salesman and most of my local shops stuff is way overpriced. I order most of my stuff from GrowersHouse or Amazon. I have noticed the cost of my Hortilux SE bulbs go up.
12” shouldn’t hurt the plants too much if the hoods are AC as long as you don’t get any bleaching or burnt pistils. I just switched from SE 600’s to LED but have yet to flower. Hopefully it was worth the “upgrade”, if not then it’s back to HPS.
You want to dial back the A because it’s NPK is 3-0-3 so it’s high in nitrogen. The B is 1-4-6 so it’s lower in nitrogen and higher in phosphorus and potassium which is essential for bud production.
The part A seems to have calcium and micro nutrients while the B does not so I wouldn’t cut it out completely but definitely try lowering the rate. If you are currently using A & B at a 1:1 ratio, try going with a 1:2 or 1:3 ratio and see if the N toxicity subsides.