Are my grow pots too small?

After 5 weeks of veg I am noticing the leaves are turning yellow and I am wondering if the roots are choking out because I used too small of a grow pot. Could that be my problem? If so, can they be transplanted to a larger pot if needed without harm to the plants?

if the leaves are turning yellow and curling under at the tips ur plants may be receiving too much heat and sunlight

Yes you can transplant them safely. You should wait 3-4 weeks before putting them into flower though.

ideal would be 3 to 5 gallons. yellowing leaves usually indicated a N def.