On Bus Times (which for some reason, isn't showing any Arriva vehicles on the map and the main fleetlist page shows the last tracked times as around 2-half 2 yesterday but the vehicle pages do have their tracking data from today) lists today's X93/X94 allocation as
Departures from Middlesbrough
0750 X94 (Redcar working): B7 7426
0850 X94: B9 7402
0920 X93 (Whitby working): B7 7424
0950 X94: Pulsar 1436
1020 X93: B9 7406
1120 X93: B9 7401
1220 X93: B9 7404
1320 X93: B9 7405

7425 is showing as last being used last Tuesday (1st September) while 7403 was out on the early X94 working yesterday.