If you dont have holes... how does your water drain? your water must drain some how.
Another way to know is if your not stressing your plants in any other way and, they seem to have not grown for weeks on end you are prolly root bound.
Let me explain "root bound" for you in case your confused root bound is where your roots have run out of room in their search for more room to get bigger, In turn you roots begin to go in every which direction untill they get tied in knots.. by then your plant will not be growing anymore and sometimes your leaves will turn yellow I think.
Hope that helps