pot size

Does the pot size (container) have an effect on the plants? ATM, i'm using an 4" (not sure) and have been growing in them for a month. The plants right now are about a foot tall (smallest being around 8"-9"). Is it too late to change the pot size or will they be fine? THanks in advance.

a good rule of thumb is 1 gallon of soil for each foot of height ur plant grows

^^what cotton said

you're probably gonna need to transplant to a 3-5 gallon container depending on how big you're growin your plant

is it safe to transplant them even though they been growing for over a month? will there be any side effects? any specific procedure i should take into consideration?

they'll just go into shock for a day or two where growth is slowed which is normal with any transplant but being over a month old shouldnt make a difference

just be careful not to cause too much root damage, ive found it helps to water them a day or so before the transplant which helps the soil/rootball stay together

just take your time and be very careful, give it a good water after and you should be fine