Bottom fan leaves cupping up/ tuting sideways

Hey I am 5 weeks in to flower and aftet a day of not watering I noticed that my big bottom fan leaves are starting to cup up/roll over sideways and some of the upper new growth has a very slight cupping upwards.anyone know what could be the problem? Domt think it heat/light stress as the worse of it is at the bottom and havent run in to this problem during my geow yet
Will try get pics up at some stage

often too much of the wrong fertilizers burning, or jacking your ph locking out your needed nutrients. I've seen
pure water fix this with a little time. water only when dry and light.
more guesses to come for lack of pictures?

Yea wont be able to get any till later my lights are on and they to big to get out my door.the leaves are still green so hopfully nothing to major