It could just be something related to the food or their regular intestinal sloughing. I give my chickens tomatoes when it’s hot and I don’t notice any change in their droppings from that, though. I’m glad you haven’t noticed anything further amiss — that’s a good sign.
My understanding is that ivermectin has a disputed efficacy for worms but is good for biting insects — mites and certain kind of lice.
I wouldn’t worm monthly unless you lived in a tropical wet warm humid place and had noticeable ongoing issues with worms. My practice is to worm my flock for the common intestinal worms on the spring and autumn equinox and alternate worming products so a resistance doesn’t form. I will also worm them ad hoc if I see symptoms or evidence of worms. Some people don’t worm their chickens at all unless there is evidence it is required. It depends on your philosophy and experience.
Depending on which product you get will determine the method of administration. I’m in Australia and the most commonly available wormer for chickens is levimasole which goes in their water. I also got fenbenzadole which is a powder that mixes into their food. When my girls got tapeworm I used praziquantel cat worming tablets because it isn’t approved for chickens here.
Garlic and pumpkin seeds and papaya seeds are all good things to help chickens keep a manageable worm load too.
		
		
	 
Lillith37,
 
Your advice has proven to be impeccable so far, and even agreed to by my vet's vet tech, and considering I live in a small town with one of the best Vet Tech colleges in Texas  .... wow, that's a big Kudo in these days of "pharma RULES", if you know what I mean.
 
I did a LOT of reading, both here and at many other sites, including Texas A&M and Brazoria County Texas AG Extension Agent discussions.   I settled on administering "SafeGuard" pellets with the flock's food, which is is what you referred to and known here in the U.S. as  Fenbendazole.   The challenge is that it's difficult to figure out the dose for a flock with mixed ages and sizes, but the good thing is that it's not particularly dangerous, and within accepted parameters, doesn't recommend not using the flocks eggs.   I ended up going with an average of a small handful of pellets to 5 lbs/chicken feed and mixed it in the general shared feeder.    (Fortunately, I had just switched from a separate PVC tube feeder system that wasn't working well in humid sub-tropic conditions.)
 
Long story short, all of my flock seems to be more healthy and laying maximum eggs, (but that's also likely to the change in daylight and warmer temps), but I've had ZERO orange-red poop balls in my shavings scoops so far after a week of that feed and "SafeGuard" mix.   Now I'm moving them back to just normal feed.
 
The gist of it is that my girls are going great right now and appear to be really healthy ...... (IRISH KNOCK ON WOOD!!!)  
Also, because I want to avoid mites and lice, I've set up a new "dust bath" circle for them with just a small dusting of the "old style" "Seven Dust" with just the natural chrysanthemum extract, (not the "kills 160 types of bugs" stuff), and some organic garden lime at the bottom of my coop after a big spring cleaning with some baking soda and a bit of bleach added to the spray-out after clearing the whole coop ..... letting it dry out ... then putting the organic garden lime, some Seven dust sprinkling, and then the clean shavings back in.
All is going very well right now, so far, Lillith.
 
Now, I'm hearing from others I still need to dose my girls with Ivermectin on a regular basis.   I have no issue with Ivermectin in horses, or humans.   But I want someone to explain to me for what reasons I need it for my flock and need to throw their eggs away for a month or so while doing so.  I've never found Ivermectrin to be found adverse to consuming ..... but these are different times with some different people.
 
I can do without my eggs ... but I'm in a somewhat rural area where the Food Bank really appreciates and needs the egg donations I bring them ... that said, I only want to share healthy and safe eggs.
 
Hmmmm.   Maybe you have special ideas you have on that topic.