Over the last couple of weeks, I have had to take Rhu to the vet and I know many other dog owners have had to as well.
By speaking to the vet, grass or mud seems to be why many dogs are sick and have had the runs. If you find your dog 'not themselves', starve them for 24 hours and make sure they have plenty of water. Check when you take them to the toilet that all seems ok.
If things go back to normal small meals and plain food such as chicken, rice or weetabix with water is good until they're 100% again.
If not get them to the vet immediately.