Stomach issues ?>>Diarreha

Need some advice ..So my mini horse in the middle of the summer got very bad diarrhea I mean all legs soaked in the back tail to.Extreme gas I found(gas went away in the start of the winter) .Had the vet up she said worms gave him a good dose of wormer same.Vet came back put him on Kayo pectin for like 2 weeks it got better but not completely gone.Vet thought maybe sand colic put him on sand lax still floppy poops and not as bad diarrhea but floppy .Winter came sand is all gone still had the diarrhea off and on etc..Drinks eats only hay nothing else no oats as vet said he didn't need it.Any how have asked around and no one can give me any ideas (I am done with the vet)I went down to the states a month ago and went into a feed store and asked the girl.She said sounded like stomach issues in the upper part of the stomach or something and she said try this prepro(prebiotics,probiotics and enzymes) fed it to him twice a day and his poop went back normal after a few weeks.Now stopped it and I see a change again so going to start him back on it.SO any thoughts on what I can do will I have to use this for the rest of his life?Or is there something else I can do.He is not under weight at all even when he had the diarehha.

You aleady have him on a "nothing" diet, so that's good.

His gut flora is way out of balance and all that worming didn't help. I wouldn't be surprised if he didn't need wormed at that time

Yes, plan on keeping him on the Pre-probiotic the rest of his life

I use Daily Start. One of their enclosed scoops daily. I feed it to two of my horses, so five pounds lasts a few months. You might find it cheaper than the link below.

Daily Start has Oligiosaccarides in it, which are the PREbiotics.

Digestive Supplements for Horses: Daily Start Probiotic by Equi-Shine

Nothing is going to be 100% but this stuff does help. I know when Spring grass comes on, my Arab will once again have loose manure but it won't be as bad since I've put him on the Daily Start.

Not quite what you wanted to hear but I hope this helps