it could be anything i would suggest take them both to the vets as both of them have scabs it could be a reaction to the flea treatment or ringworm which can be passed from one cat to another and to you as its zoonotic,
a vet would be able to tell you better than people on the net no matter how much experience people have, as for drinking some cats drink more than others, i dont have a fountain just bowls of water in various places round the house and one in the garden, for his upset tummy plain food like chicken and rice for a couple of days may settle it
He's had a dippy tummy for the past few days, he's not pale though. I checked his gums to find his colour. I don't think he drinks enough, which in this weather would give him an upset tummy?
Also he has little scabs on his skin, he's flea treated and has no fleas but he does have a tick, that we are going to remove when I get in from work. I think this is because we use advocate treatment and that doesn't stop all ticks. Does anyone recomend a better flea and tick prevention spot on?
And would anyone recomend a water fountain for cats? Do they work? Do they encourage them to drink.
We have another cat, she does most of the drinking, she also has the scabs but I think that could be a reaction to the new dried food we have bought them.