Translation:There is something weird in the kitchen.
Just a note, it might mostly be a font change. If you notice that Meem م is written as a small stroke under Lam ل, in the beginning of the word like in المطبخ - then no worries. This is just a calligraphic change. Some fonts on computer adapt this calligraphy style.
A month before someone mentioned, that there is something weird with the fonts. I was confused too. It's a very strange Alif in the expression في ٱلْمَطْبَخ.
Fortunately I remembered the story of Hamza of TJ_Q8 (https://forum.duolingo.com/comment/34396041/The-Story-of-Hamza-Part-I-The-Beginning)
When I understand it right we have here a hamzat wasl , also called alif waslah . The alif in ٱلْمَطْبَخ has a special diacritic on top of the alif. This alif is not pronouced at all.
But why is the font of this alif smaller and thinner than normaly? Is the alif in alif waslah written differently or is this Duolingo specific, to remind us with that small thin alif, that we do not have to pronounce it?
Nah, I'm guessing it's all just some designing issues and all. In writing Arabic we don't judge letters by thickness but rather by general shape. So, a vertical straight line, with or without Hamza, thick or thin, it's after all Alif. They put a little صـ on this Alif of المطبخ which is a marker for Hamzat Wassl as you said, and this sign, again, is not required and typically found in Quran orthography. Heck, I can't even type it with my regular keyboard (I would need to use special character addition in Word or something). I don't know why Duolingo contributors are using these characters, like this one here and the dagger Alif.