Seems bizarre to change your flying programme right in the height of the summer and as you say their programme goes back to 3 flights in September on a Tuesday.
It hasn't changed - it was always planned this way.
It may be the height of the summer in the med, but low season in the caribbean due to hurricane season.
the aircraft are utilised on more lucrative routes, such as the med or Florida (school holiday demand)
So who will be contracted out to cover this 'extra' flight ?
May i suggest that you ask your travel agent - you are the one travelling after all....it is your right to know from your agent!!