Yes, they need to be watered more often than larger pots. Especially once the plants get a bit larger, they dry the solo out quickly, and if you don't fertigate often, the nutes go out of balance and the plant suffers. Because the plant is large relative to the amount of medium, shit happens in a big hurry. In my opinion, solos are most effective managed as straight hydroponics. My current solos are coco/perlite fertigated once every 4 hours to significant runoff. They could actually handle more often than that, but maybe not with much benefit, plus I have larger pots on the same pump timer, so six times a day is the compromise. They could also tolerate, I think, going as few as 4 or maybe even 3 fertigations per day, but I don't believe that they would do as well. Fertigating frequently keeps the nutes in the medium balanced by not allowing the plant or evaporation from the medium long enough to knock them out of balance. It is extremely difficult to overwater coco/perlite, but it is dead easy to underwater this medium in solos.
The trouble with soil in solos is that fertigating often enough to deal with how soon they dry out can result in overwatering, or alternately nute buildup or imbalance because you can't water often enough. Coco is a better medium for solos, in my opinion, specifically because it allows very frequent fertigation without overwatering risk. You should water to at least 10% runoff, and if the medium you are using does not permit this to be done often enough, trouble will happen, usually in short order in solos. Having soil in the solo does little good in my opinion, it is depleted very soon due to the small volume of medium relative to the size of plant, and once depleted, just makes managing fertigation more difficult.
Good luck with the grow, I hope you manage to keep it on track.
