Some leaves starting to die / first day of 6th week of flower / Potassium deficiency?

Looks like tip-in progression rather than interveinal. but if it were N-deficiency it should be predominatly moving up from the bottom and not interspersed to start. so, take some common sense about what you've done the last couple weeks in regard to N -- if you drastically lowered it, consider raising it back up slightly. If you haven't changed much in regard to N i'd be more hesitant to blame it due to the weird progression. the curling hints at overfeeding... could be lockout of N. Did you 'boost' p or k? depending on what was provided before that could cause lockout. Trace elements are rarely not physically present, which usually means if you see symptoms of those it's related to pH or an imbalnce of nutes locking them out. Potassium deficiency is usually pretty obvious.. damage around the serated tips with some accompanying chlorosis at some point too. I don't really see this hear, but.. maybe. Symptoms are not discrete. it always takes some cross-referencing. i hesitate to give a concice simple answer because you probably have some relevant information that is not provide dhere, and it's better you work through the deductive reasoning rather than having tunnel vision reinforced by a an educated guess with less available info (from me or anyone else). make sure pH is good, consider any drastic changes to fertilier formula provided... make a conservative guess and see what happens. IF it does'nt slow or reverse, you know the change was ineffective and move on to next most-likely option. e.g. based on what i see and given in this qestion, i'd start with maybe a 10% boost to N and see how it goes... (assumes watering habits are kosher, ph isn't whacky etc - can eliminate that stuff without affecting plant)

NPK def Uw bb

You should aim for the faid at the end of the flowering Stage ( last 2 Weeks ) but for now it looks a Little Bit to early…