First, I have to say that these kittens sound too young and not fully weaned enough to have left mum. So, if they only just stopped nursing and aren't comfortably on kitten food (and provided mum hasn't died), we'd want to think about having them back to mum until they are fully weaned. That said, with one kitten showing persistent signs of upper and lower GI upset, this doesn’t support benign gut upset from overindulgence alone. Instead, it raises real worries of stress predisposing him to a bacterial or viral gastroenteritis. Or we'd also have to consider parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items (litter would be a worry as it can cause a blockage and thus signs like this as well)
With this all in mind, as long as you are sure Milo hasn't eaten something dangerous and he can keep fluids down, we can try some home supportive care to try to settle his stomach. To start, if he hasn’t just vomited (since otherwise we’d need to rest his stomach for a few hours first), then you can consider treating him an OTC pet safe antacid [ie Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid),Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet)]. Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do double check with your vet if he has a known health issues or is on any medications you haven't mentioned. Though if he cannot keep it down due to nausea, that is usually a red flag that we need to bypass his mouth with injectable anti-vomiting medication from his vet.
Afterwards, we'd want to keep up on the mild if we can and can also start small meals of a light/easily digestible diet. Examples you can use are boiled chicken, boiled white fish, or meat baby food (garlic/onion free). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the upset gut. Therefore, it should get more nutrients in and result in less GI upset. Fiber (ie canned pumpkin) and feline OTC probiotics (Fortiflora, Benebac) can also be used here to firm the stools quicker and settle the gut. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning slowly back to your normal diet.
Since dehydration is a risk for kittens with these signs, we need to keep an eye on hydration here. To ensure Milo’s not becoming dehydrated, there are a few things you can test at home. Further to checking for gum moisture, you will want to make sure his eyes are not looking sunken and that he doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have him seen before this becomes an additional issue (especially as it is often dehydration that makes them feel unwell).
Finally, as long as there is no blood in those stools, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure for infectious issues; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p)). This is available OTC at most pharmacies. Avoid Imodium, Pepto Bismol and products with aspirin/salicylic acid as those aren't cat safe. Otherwise, Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (all OTC at vets, pet stores, and even Amazon) would be another option. All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria. So, these can be used as a short-term means of soothing his upset GI.
Overall, there are a wide range of agents could trigger the signs we are seeing. Since Milo is so young, we need to be very careful here. You can keep him on the milk and also use the above. But if we cannot get him settled in a few hours, he cannot keep the above or the milk down, appears dehydrated already, or becomes weak; then we'd want to get your local vet involved. They can assess his hydration, rule out fever, make sure there is nothing in his stomach that shouldn't be there or any sinister viruses present. Depending on their findings, his vet can treat him with injectable anti-vomiting medication, fluids, +/- antibiotics to settle this before it can take a toll on him.
If you have any other questions, please ask me – I’ll be happy to respond.
**Please rate me by clicking on the **stars** at the top of the page as this is the only way the site credits me for helping you. Thank you!: )