BRAAAAAAAKES! :o (and how to improve them).

For a quick fix/help you can put a large flat blade screwdriver between the pads where the centre pin passes through and prise the pads apart. this pushes fluid and air back to the reservoir. BUT THIS WILL NOT CURE IT. Your best action is to replace the master cylinder. As stock it is 14mm. Most others use 5/8". This is almost 2mm bigger in diameter and makes a massive difference. 1st thing we used to do to our Jack Lilley race bikes.. We used m/cyl from a Yamaha yzf750 but Jack Lilley now sell the part as a brake upgrade.
Don't bother with separate fluid hoses. it makes no difference at all.
BTW best pads for your bike is stock Triumph units. Designed to work with your discs in association with Nissin. And they are kind to the discs too.
BTW2 I don't like putting a tie wrap around the lever overnight. It does not last and puts a massive strain on the seals etc. you are just masking a problem.
yam part number 3GM-W2587-50. This buys just the m/cyl, not reservoir or lever etc, that some like Kawasaki do although they are the same part.
Some are also available on ebay 2nd hand, but buy wisely.

Another alternative is the radial m/cyl used by triumph on Daytona 675 or street R. But these will need a replacement hose and lever.