my house has old warped joists. Is joist blocking safe?
I would sister several of the joists, then add solid blocking in each span. The blocking might not be critical, but the ceiling is now open so why not? Solid blocking does not need strapping across the bottom.
Look closely where the joists meet the load-bearing wall at each end. A 2x6 ledger might give extra assurance. Look at the rest of the floor structure for any splits, sags, movement, etc.