Probiotics the Key to Weight Gain?? Helping w/ Ulcers??

a bit of background:
My now 11-y/o (in April) gelding has struggled w/ stomach/intestinal ulcers almost his whole life. They initially rose their ugly head when he was 4 years old & first properly getting started into “real” work, which coincided w/ when I first moved him away from my parents’ property where he’d lived his whole life (well, since I got him as a weanling) up until that point. His initial bout of ulcers was rather severe, graded 3.5-4/5 by the vets who did his scopes, took 90 days of UlcerGard treatment (& 4-5 months off work) to get properly cleared up, and left notable scarring in his stomach. In addition to clearly having a lot of tummy pain, while he’d previously been a very easy keeper, he lost a lot of weight & became very “scraggly” looking while we were trying to get the initial ulcer flare-up under control, despite excellent care/feeding/management. Since then, I’ve made a point of trying to make sure he gets treated (30 days at a full dose + 30 days at a half dose) w/ generic omeprazole or omeprazole/ranitidine paste at least once a year, and in doing so have been able to keep his ulcers -mostly- under control.
Unfortunately however, I’ve recently fallen on hard times, and was unable to work for a good while due to physical health issues I was dealing w/. (though I am doing somewhat better now & have recently started looking for work again) Subsequently, I have been unable to afford to give him his annual course of omeprazole – he was last treated in 2015.
He seemed to be doing pretty well & fine in regards to his digestive health, up until this past fall …In late fall, he started showing clear signs of a bad ulcer flare-up…and the weight started dropping off. For a good while prior to that, he was staying quite fat, practically on air. When he started acting “ulcery” & losing weight, I made modifications to (& of course increased) his diet, and starting giving him 4 oz of high quality aloe vera juice (Lily of the Valley whole leaf juice w/ “Aloe’s Orb”) twice a day in his feed. It was slow going, but he was gaining back some weight. Then a couple months ago, I got what I guess was a “bad” batch of O&A which caused him to colic for the first time in his life – a severe gas colic. The combination of the colic itself and having to reduce his intake & slowly increase it again afterward resulted in him losing all the weight he’d gained (and then some, honestly). And for whatever reason, he was just NOT gaining any back after that. It was seriously concerning me. Despite getting ~12lbs alfalfa/grass mix hay, ~4-4.5lbs Purina Ultium concentrate, ~3lbs alfalfa pellets, ~3.5lbs (dry weight) pelleted beet pulp (<<-- spread out into 5 small meals over the course of the day), and being turned out on grass 8+ hours each day, he looked absolutely AWFUL – as if he was being starved.
I started trying as hard as I could to scrape up the money needed for a full course of omeprazole treatment, but in the interim I happened to pick up a tub of Probios while restocking my feed supply at TSC. I figured it certainly couldn’t hurt. I’ve given him probiotics before in the past, but only while traveling (he’s sometimes prone to nervous diarrhea in those situations), and for fairly short stretches of time after omeprazole treatment in order to replenish his supply of good digestive flora.
but OH. MY. GOSH.
Those probiotics clearly seemed to do something amazing! I have never in my life seen a horse gain weight SO quickly. Over the course of just 4 or 5 days after starting on 10g/day of Probios, I swear he must’ve gained at least 100lbs! The transformation was downright shocking! He went from looking (to me) like he was literally dying, to looking perfectly healthy – no visible ribs, nothing – in well under a week.
His tummy is definitely still bothering him a bit, but there has been some noticeable improvement in that regard too. So I’m thinking I’m going to try Gastrix (which comes w/ glowing reviews from my vet & is only about 1/4 the cost of even the generic omeprazole) for his ulcers now before going to the omeprazole paste, because that’s something I can actually afford right now.

but I was just wondering…it seems to be so…but is this sudden & drastic improvement purely a direct result of adding Probios? I would’ve never imagined something so seemingly small could make such a MASSIVE difference practically overnight!
Has anyone else had an experience like this w/ probiotics?

Regardless, I am just so happy & so relieved that my beloved gelding seems to be finally well back on his way to good health & is doing so much better all around.