Indeed. This will be the last time my solos are on the same reservoir as my full sized pots. Even when they are both in coco, the tighter pots behaved differently later in the grow, particularly with pH. In this grow, once the roots in the solos packed in, the pH drifted up, in the large pots, it drifted down. Late in the grow, the two pot sizes need different fertigation pH, IMO, so next time, separate reservoir.
I know that lots of experienced growers say don't sweat the runoff pH, but I beg to differ. If the runoff is out of bounds, it means that the medium is too, and absent doing something about that, trouble will continue. IMO of course.