Yellow tips seedlings magnesium?

Thanks for uploading the photos. The indeed look a little stunted, and I can see where one was stretching for light, but I don't see anything irreversible! Depending on the soil environment your ph may be a bit high. 7 may work for a super soil, but if it's a soilless mix that ph is going to be really high. Twisted, stunted growth usually makes me worry about cal-mag, but that can depend on a lot of factors such as the growing medium and water source. The pots are very large, so make sure you are not overwatering. Center watering small amounts is key in this case, but don't overdo nutrients while only watering in the center as you won't be able to "flush" nutrient salts out of the soil. I would pick up a suitable vegetative fertilizer, like you were saying. Mix and ph it to 6.5-6.7. Keep the concentrations very low at first, like less the a quarter of what it says on the bottle. If you are measuring ec, .4-.6 is where I would top out. If you are able to transplant to a small pot for now, doing so has risks of damaging the plant further but could make it a lot easier to fully water through with nutrients and maintain a good watering regime at this stage. Your call on that front. Hope this helps, and I hope those sweet babies recover well! Happy growing 🙂