Bye bye GB going

Ok i have added a Smarty to sim to my phone where i have a Giffgaff sim aswell. Down wales i use Data in caravan. Normally Giffgaff lasts a good 3 weeks with 25gb.  I added 100gb a day n half ago on smarty.  Looking at history and gb left it saying i used nearly 3 gb in a day, hardly used it🤷🏻‍♂️.  Why does data go quicker on smarty?? It definitely is going faster. I thought it would be the same surely as others. Anyone?? Cheers