Second ward.
Absolutely not. As an Auror I try to keep myself from jumping to conclusions based on small coincidental bits of evidence because that is certainly how you get things wrong, but it's certainly not wrong to be suspicious in this climate. Had we been actually able to investigate properly we likely would have been looking into Mr. Montague after Misters Weasley shop was vandalized given the history there.
I would caution against allowing yourself to be paranoid, but you assuredly should be keeping your eyes open.