The key points of this query are specified as
(Presumably, there has been no change in the connection of the "original" set-up to the supply.)
While the OP states "bulbs are good", the foregoing seems to be completely inexplicable to me - UNLESS somewhere in the set-up process a relatively high voltage has been applied to the "original" 7 lights and they have "blown". I can only suggest that one or more of these original 7 lamps be tested, to see if they are actually still operative, before proceeding any further.
It seems that the OP is saying that the new set of lights - attached to the supply at the end of a previously existing set of lights - is now working BUT, the previously existing set of lights, along the supply to the new lights, is now NOT working !
(Presumably, there has been no change in the connection of the "original" set-up to the supply.)
While the OP states "bulbs are good", the foregoing seems to be completely inexplicable to me - UNLESS somewhere in the set-up process a relatively high voltage has been applied to the "original" 7 lights and they have "blown". I can only suggest that one or more of these original 7 lamps be tested, to see if they are actually still operative, before proceeding any further.