Guys, I have to apologise: Firstly because I kept you in suspense longer than I originally thought and even more because I didn't find the certainty that I always set for myself as a benchmark.
... but you're right, enough waiting; so first just the facts and then my interpretation: I have information from a very reliable source that at the end of August four J-35/31s were spotted simultaneously on the factory premises in Shenyang.
The interesting thing about it - and this is the weak point - is that I'm not exactly sure what they are exactly: I actually thought that the J-35 could be distinguished from the land-based version J-31 or whatever it's called, mainly by its larger wingspan and slightly different wing geometry. The gap between the wing and the tail unit is not visible anyway due to the low resolution.
Unfortunately, this is not as clear as I thought, but my "impression" is that three of the machines are the same and one is different... it's just that I would assume that only one is a naval version J-35 and the other three are more likely J-31 (?).