I feed my cats three times a day. I split a 70g tin between them, and a handful of kibble on the side.

If they are getting roughly 100g of wet food each, how much dry should I be feeding along with this?

They get either Almo Nature, Porta 21 (they'll only eat the chicken one) or Tesco Finest. As Almo Nature is complementry, should I feed more dry in proportion to this?

I can't find feeding guidelines for Porta 21 anywhere. I worry that I'm not feeding my cats enough or too much. My two only seem to eat what they need, so I use that to judge what to put down for them.

Another question -
I'd like to feed a totally wet diet. Would it be bad for my cats to only have Porta 21 pure chicken or Tesco Finest Tuna? They are SO fussy and these are the only complete wet foods that they will eat. Would they get bored with this, and is it bad for them to feed exactly the same thing day in day out?

They are nine months old now, and I think maybe I should take them to the vet to check their weight and put my mind at rest.