Cupping leaves, moisture or root bound? Thoughts please?

These are my 2 Cheese ladies, under a 250w dual spectrum HPS, and they have major Taco leaves. I've done a bit of reading, but can't confidently diagnose what is causing it. They were transplanted from 3l to 7.5l pots 10 days ago (having filled their 3l pots nicely in a week and a half, circling the edge of the soil nicely, but not excessively) and have had these leaves for the past few days. Temps are around 22-25, and humidity is at 45 right now, which I know is a little low for veg, but waitin till i get my new pH pen later, and will give them a good soak, which will help. Even when humidity was 55, I still had silly taco leaves.

I can't believe that they are root-bound already, and have seen many bigger plants in pots these size. I will flip in 3 days (14 after repot), do you think the pots are big enough, considering they are an 8 week flower plant, and I imagine don't do much rooting after the first 2 weeks of flower.

Any help would be greatly appreciated

Someone? Anyone?

They won't be rootbound dood, i finish most of my plants of in 7.5 lt pots.
Looks like they may be a lil overfed? what soil are you using and what/how often you been feeding them Hetty?

have you been feeding them, to me they look like they could use some nitrogen

They look magnesium deficient too me...they are praying for magnesium.

LOL.. on second inspection i was gonna edit my post to add it could actually be a Magnese def.. give em a pinch of Epsom Salts and see if that perks them up a bit dood

Thanks for all the input, I had noticed the Mg def, and have bought a new pH pen today, and gave them 300ml each with some Gold Label ultra Mg in it, at 6.6pH so hopefully that will sort out the defs (being that Nit can't be used properly by the plant without Mg). They were repotted into a mixture of Biobizz Light Mix, and All Mix, with some extra perlite ten days ago, and have had no additional feed since birth, just the nutes in the soil from each re-pot.

I'll prob feed again in 2 days with Mg and a little BioBizz veg, and take see how they get on.

Never had Mg def cause leaf curl before, so didn't connect the 2