Hmm looks like how my girl looked while back when I had mag and N diff.
Could b that mate but I'm pretty new to this game, but the leafs do look quite pale n looks like it was starting before u begain flowering.
But I'm just going by my experience, u may wanna wait for a more seasoned vet tho.
Good luck
i have the exact same problem. im also in week 5 of flower using hessi bloom and phosphourus @ half strenght + hessi supervit 1 drop per 4.5l of water
i thought it could be the tap water im using, so i got an ro filter which will hopefully sort it out?????????