Yeah, the difference is only minor, some variation in fuel amount can do that also. And beefier tyres are somewhat more heavy.
Mine has no sunroof at all
The California top definitely adds some weight as being like giant sunroof, and even standard sunroof assembly weighs quite a lot.
Also, my car has non-sport seats which probably are bit lighter, will be replacing those also in some point with proper buckets. Target to final weight is under 1200kg with M52B28 engine, ZF box, complete rollgage and other race equipment. I'll convert the car to six-banger probably after this season, have no time to do it now if I want to drive this summer.