That must be very worrying.
Keep a close eye on them and if you are concerned they are getting worse ring 999 for advice right away, they can give you help or connect you with the doc on call who can advise also. If you are really worried, take them to A&E. Better to be safe when it comes to this.
Its awful for the little ones, hope they feel better soon and hope you ok too, cannot be easy for you looking after them and fretting about it as well.