Should I be feeding my clones in veg? I keep them ...

If the soil is fertilised then you shouldn't need to feed anything , and if you truly must feed something to keep yourself busy try enzymes or humic & fluvik acids . They seem slow from being root bound because they stayed too long in those solo cups. You should be checking your incoming pH if you can, might be a bit high if they are showing the start of Cal/mag deficiency , what you can do if you have any on hand is make a foliar spray with it , spray until dripping wet every day for 5 days and see if they "recover" I put that in quotes because it doesn't seem like very serious. Hope this helps ! 🚀