Noticed small brown spots kind of center of leaves...

For the little brown spots on your leafs is starting sign of PK deficiency most people refer to it as "rust" . You must remember that when your flip your lights from veg to flower your plant is always going to need a good boost in PK to help facilitate the transition from veg to flower . Its trying to use up all the PK it can from the medium to from up the flowers . I would also advise that you use some CalMag supplements during flower , this will help a few different things but mostly help keep the plant on the level so that it can keep pushing forward making big nuggy nugs . The CalMag helps prevent the yellowing in the veins of the leaf as well as getting those little red/purple stems .Mostly your problem stems from not having any Potassium and Phosphorus in your mix here ( thats PK ) and this will lead to the little "rust" spots you see on your leaves . I would advise that you start using your bloom solution as soon as you can to slow and then stop the damages that have been done so your plant(s) can be rocking and rolling :) . I hope this information helps you a long your journey to becoming a grow master ! :D -Happy Growing!