
Among other things I feed NFD which is why the mention of dry kibble was confusing :)
As it's only been one night that your youngster has had a problem it's probably premature to assume it's something in his usual diet which has caused the problem. Most likely he's gotten hold of something he shouldn't (or possibly had a few too many treats/titbits?) which has slightly upset his system and this should settle within a day or so of bland food, little and often :)
As he's been having the ND supplemented with beef for several days then it seems unlikely that is the cause although it may well be that you're increasing the quantity of his food to a greater degree than his tummy can cope with.
I feed a mixture of raw and moist completes but when starting out found the best way to supplement a moist complete for weight gain was to given raw chicken wings or thighs as a separate snack in the evening following their normal daily quota of anything else :)
regards, Teri