Hey O !
I know Jacks has a pretty good reputation. So I think you are OK there.
The red on the stalk or stem is sometimes genetic
and/or sometimes from
low magnesium. I see magnesium in the Jacks ferts.
Honestly I dont have enough experience to say if it is
enough Mag in the ferts, but it sure as shik should help.( fort what it is, I use epsom salts as a mag boost in my soil mix, but it is all good)
Not sure how weak your stems are, But, I have heard to use silica/silicon for strength in the stems, not sure, I have not really had a problem with weak stems. I got some silica powder here somewhere, I am not sure if it has helped, i use so little of it. My buds probably are not big enough.
Any who What I wanted to say is, seeing that Jack's classic brought back good memories. Back in the 80s when I did guerilla growin.
I used Peters professional 20-20-20 for the first half of the season and miracle grow 15-30-15 for the second half. And it worked good.
We would start at 2 -3 weeks half strength then hit it with full strength mixture, then the same for the mid summer switch to 15-30-15 half strength at first then BooM full strength.
We really had no clue what we were doing. I prolly still don't.
looks like buds are a blooming, Nice!!