Istanbul Xist Brilliant Crashes cracking after 7 months

I bought two Istanbul Agop Xist Brilliant Crashes (16" and 18")in March this year. Yesterday i've discovered a crack close to the bell of the 18" crash and just now i've also noticed a small crack in the same spot on the 16" crash. I'm using 5A for sticks and i'm also not playing them super hard or "beating them up", but rather just playing them normally. I'll go to the shop i got them from and ask them about the guarantee (Istanbul themselves says that they give you 12 months of guarantee) after Christmas but i've wanted to get some second thoughts on this beforehand.