Great grow. I wasn't able to follow real-time, but I'm making up for it by reading through the thread.
Couple of thoughts on the whole TLO/LOS, when to topdress, etc, etc....
Check out ''Mr. Canucks Grow '' Youtube channel. He uses ('sponsored' by) Gaia Green products and makes ultra-high quality (and funny) videos explaining and demonstrating use of the very same products, throughout his grows, albeit not in SIPS, not yet. (I give it 3 mos. max before he posts a SIP vid!) Nonetheless, my feeling is that you might get some things answered for you there in a convincing and entertaining way.
Worm castings. I realize you have some immediately available ferts in your mix but container gardens can really struggle to maintain microbe populations. Those beasties that are down there turning turds into mineralized plant foods, etc, need our constant support, even in SIPs. I would recommend a hearty dose of microbe-dense wormcastings in the original mix, then letting that mix sit a couple weeks in the watered SIP if possible (with a plastic or cardboard cover blocking light and retaining moisture. Keep the whole thing at room temp, minimum. Then, whenever you do topdress, include a generous portion of wormcastings. The castings themselves over some nitrogen but they contain phosphorous solubizing bacteria that'll feed your plants lots of P and micro-nutes. I also like to make table-top, wormcasting teas, in these large 2 gallon, black plastic bottle/cannister, like those ones the expensive supplement store sell men so they can get THIC! Check your THIC neighbour's recycling box on recycling day for those, they keep all UV out. Bubbling water and wormcastings in these for 48 hrs, with a little brown sugar, will explode the microbe population. Pour some on the top gently, slowly, but not enough so lots leaches quickly into the rez. It can wash unwanted biomaterial from the soil matrix down there, stuff that might start to putrify. Just pour slow. Another major consideration for microbe populations is temperature. So you'll wanna know what's the usual temp in your SIP rez? Is the SIP sitting on cold concrete? Just a few degrees F upward can really boost populations if you still have the 'ceiling' to do it.
Tons of biomass, stalks and leaves, is def a SIP feature, not a bug, but they are the support system for buds!
I'd apologize for the word walls, but I'll likely just do it again to someone else tomorrow...