Thank you - would you recommend to feed fondant as they’ve been robbed? If so how much ? ThanksYou've given far, far to much space. That hive is the equivalent of two 14 x 12 brood boxes side by side. The bees will never be able to keep the hive brood area at the optimum temperature. Start with a brood area plus two or three frames and expand as the colony increases in size. The Dartington should be used with insulated end boards to contain the size of the colony.
See the Omlet Beehaus (plastic Dartington) guide for management of a long hive.
I agree with previous posters that the damage looks to be caused by a rodent. You will need to sterilise and re-wax the affected frames. Bees are reluctant to use frames contaminated with rodent urine. https://www.omlet.co.uk/files/public/omlet_guide_to_keeping_bees_and_beehaus_instructions.pdf