Our kitten is 5 months old and we've had him since 9 weeks old. Ever since we've had him, his poos have been really soft (he's constantly getting his tail in them
) and sometimes liquidy.
I went to the vet and was given Royal Canin gastro-intestinal food which definitely helped - but a few days after we've finished the box, his poos are going lighter and softer again 
What can I do?! Have tried most supermarket brands and apart from Tesco dry kitten food, everything else seems to affect his little tummy 
Any thoughts? Should I order a selection of better quality foods from Zooplus or similar and keep trying? He has regular worming and flea treatment.
Thank you 