Yea 3 of mine are about the same age (planted the 25th) and for the ones that were leaning to the side, I just stuck a toothpick about a mm into the soil and let the plants lean into it. Within a day or 2 I could take the toothpick out cause they straightened up.
As for nutes, if you're growing in soil with any kind of NPK in it, you wouldn't need to use any nutes until they've been in the soil for 2 or 3 weeks. I'm growing in the same exact cups with a soiless mix, peatmoss with perlite or vermiculite and don't plan on nuting them until 2 or 3 weeks after transplanting them in 2 gallon pots, which I'll do within a few days as the catyledons are starting to yellow and curl up, which is a sign of nutes in the current soil running out.
Hope that's accurate and helps.. I think it's accurate anyway
