Ahhh yes, I suspect it could be any of those situations (compost, berries, lake weeds) or all of them. There are many cases of birds getting in to compost and getting botulism. The heat from the composting kills bacteria on the insides - but doesn't effect the edges. So for poultry, it really is best to keep some kind of wire up. Our own speckledhen can tell you how important this can be.
Since she's perky, and since the above mentioned situations can include mildews and molds that are good for the process of composting but not so good for the process of digeston, you might do a gentle cleansing of all their digestive systems to clean out anything that might still be in there. It's not necessary to do a flush like you would for botulism. But something gentle to just get the "yuck" out and give the digestive tract a good clean slate for the good bacteria in the yogurt.
It's as simple as making some sort of mash for them and include 1/8th a teaspoon of molasses and a cup or so of applesauce. Oatmeal makes a great 'base' for this (cooked). Add 3 tablespoons of yogurt do that - it'll serve three to six hens. The molasses gently flushes the system, the applesauce pectin both cleanses as well as acting as a PREbiotic to the PRObiotics/yogurt (i.e. feed for the living bacteria to make them happy so that they colonize and flourish), and they just like oatmeal.
I would also make sure that you have a good source of oil vitamins around just in case - like cod liver oil for example. If they get into mold/mildew, it causes oil vitamin deficiency. A regular vitamin/mineral package should work since she's better (water application).
Of course, I'm going to recommend oyster shell as a calcium source because it's more bioavailable, more easily absorbed into the blood than egg shells.
It's the standard and has been for years because it so easily gets into the blood through grinding in the gizzard. So there's my official recommendation. /wink
I'm very glad to hear that she's doing well today - that's a great relief!
Incidentally, only feed amprolium medicated feed., I would not feed anything with an antibiotic (BMd for example). Amprolium isn't an antibiotic, is only an anti-protazoa medicine.