Hey Hemi, been away & busy for awhile, trying to play catch up now. Man, sorry to see the Girls got hammered from your pH problem during your out-of-towner. You did a great job recovering, though. Wish I could say it won't have a large effect on your yields, but it does look like they stunted a bit even after your stellar recovery. Not a loss, just a little hurt. We all been there / done that.
Your pH creep dilemma (seems to me) sound like a water problem; more specifically lower levels of calcium, and to a lesser extent, magnesium. The fact that
your dirt-grown plant was not affected seems to reinforce that. Most dirt blends have a healthy supplementation of calcium that acts as a natural buffer to higher pH drifts.
I forget too easily, don't recall what part of the world you're in, but if you are in an area where water is naturally soft, or mechanically treated by the water utility or an in-home filtration / softening system, this can lead to some rather hard-to-diagnose problems. But one key symptom in my experience has been pH drift in an upward direction.
Water softening replaces cal-mag with sodium ions, which keeps ppm's high, leading to a false sense of security that your water has sufficient cal-mag. Most nutrients have some pH buffering capabilities, but calcium doing an especially effective job. And while many base nutes have cal-mag supplementation in their micronutrients, it's usually not sufficient to make up for the loss.
Hard to diagnose? Yes, totally. You can look for calcium deficiency symptoms - spotting on the leaf portions most exposed to light; or magnesium def's - yellowing between veins on lower / older leaves. But the real problem with diagnosing this lies in the fact that cal-mag deficiencies affect uptake of other nutes, and cause pH problems which can manifest as practically ANY deficiency symptom. One way to help diagnose this, too late to do anything but good to know for future grows, is to closely examine the roots after the plant's harvest. Lack of cal-mag will result in a poorly developed, wispy root system. But the only way to accurately diagnose this is to have an extensive water analysis done on your water supply. If you're interested, let me know, I have an excellent source for these, but plant to lay out about $60 USD for the analysis.
I always feel the more you know, the better your crop will be, but $60 is halfway to a decent RO system. So if you take the prevention route, RO water with cal-mag supplementation will pretty much make these problems go away. These days I see downward drift if my nute strength drifts too high (too strong for the plant I'm growing results in extra buffering), but I never see up-spikes anymore unless I dilute my nutes a lot with no cal-mag supplementation. So RO is food for thought, or another area to spend more money. This is an area where you can do without it, but you will see more consistent results once you adapt to it.
To comment on Lunarman's post as well, re. high stress training affecting auto grows - I can't agree more. The closest thing to high stress training I ever do on my auto's is leaf pruning. NO topping EVER. And while a lot of growers seem to do well with supercropping, I have stayed away from this as well. The desire for a level multi cola structure that prevents the main cola from dominating the plant's growth is, in my humble opinion, the key to great yields in an autoflower environment. Probably in photoperiod grows as well.
Lunarman, If you need a few hints, look at the latter half of my light intensity thread where I've pictorially documented my latest single-plant grow of a TH Seeds Auto original Bubblegum. I went HID lighting during veg and transition to generate about 20" of stretch, then did LST training to pull the main cola down and open her up so that all secondary bud sites get good exposure to the light as well. I'll be posting an update pic shortly, day 41 and already filling out to a beauty.
If you want a more detailed illustration, check out the LST tutorial I posted on Nosias' thread: https://www.autoflower.org/threads/fast-buds-and-sweet-seeds.64526/page-10
post # 98. This technique results in a level, open canopy with almost no primary cola dominance. The ONLY issue I have with this technique is that it requires some stretch of the plant during veg / transition, to open up the plant so all the buds get a healthy share of light. A no-stretch plant stays so dense that the bud color never fully develops on a great part of the plant.
OK Men, onward with more catch - up to do. Be seeing ya around the forum.
for all the notes and advice. It is appreciated. 
