Poor SG level on stout

Hi there folks - just wondering if someone here can help. I've got a Muntons Export Stout + Muntons Dark Malt on the go, onto the 2nd stage fermentation but after two weeks at approx 25oC.
Problem is the SG's still at 1024. When transferring from teh 1st fermentor to the 2nd, this was the SG but activity was low so I pitched in more yeast.
I've made this brew before a number of times, with a final SG of approx 1012.
Any advice?

Have you used the same methods and fermentation temps as you used before to get to 1.012?

I've seen a lot of posts on here regarding FGs of around 1.020 with extract recipes - maybe the extract you used in the latest batch was less fermentable than you've seen in the past.

munton's extract is reportedly highly fermentable.

just checking, but you aren't using a refractometer for your final gravity reading, are you?

The temps may have varied slightly, but only by a few degrees within the acceptable brewing range (18-30oC). The comment regarding "extract recipes" (kits?) is interesting, I've had this before with other types of beer, but very early in my brewing career so passed it off as beginners un-luck.

I'm using the same hydrometer as I've always used.

Which yeast(s)?

At 70 degrees mine is on the final leg in the primary but it was 1.073 before i had it started fermenting but i used coopers stout with 5 pounds of muntons dark malt and other sugars. dont know what the reading is going to be when i rack to the secondary. Depending on your fermentables besides the malt the reading should of been am little bit higher thats my opinion.