In a solo party cup, if you burned little holes in the bottoms for drainage and you see roots poking out of them, you might wanna just pop the dirt ball out and take a look. Be careful though. Be gentle cuz it can be a bit of a bitch to get that to break free cuz of the ripples in the lower part of the cup. At least thats what i find. If the roots are everywhere and a thick ring of roots at the bottom, thats ready to move up a pot size or 10. I go from solo cup to 3 gal fabric pot. I pack the soil in the pot and bury a empty solo cut in the soil and back fill. When it's time to transplant i remove the empty cup and have a perfect template for the root ball. I dust the hole with fungi, and dust the rootball with bacteria, and drop her in, give her a little press into the soil, then give a little water.
Transplant shock is typical. The plants dont like being fucked with at the root level and they'll tell you that after transplant. Droopy sad looking plants are often the result. Don't panic, it's normal. They will bounce back in a few days to a week.