I think 18" was a bit too much for the plants...

Its hard to say right at this moment due to the plant being so young , but generally what will happen is that the plant will slow in growth because the roots are forming up , being as you planted it in a bigger pot right away the roots are growing sideways instead of downward because there isnt a "wall" to force them that way . Your plant will be fine and it will explode in growth soon enough . The yellowing that you see is from overwatering , based on the stats that I see your giving it a cup every 24 hours which will lead to such an issue . 1 cup of water will last you 5-6 days for a plant that big . You wanna ensure your plant goes through whats known as " dry - wet " cycle this will ensure the roots expand because they are looking for water , if your medium is always moist the roots dont have to expand leading to less root production . A good way to measure if your plant need water or not is to stick your index in the medium up to the first knuckle if its dry then you need to water if its moist then you can still wait . When they are young like that remember less is more in the sense that they are really easily over watered when they are young , so its better to give less water but more frequently if you have too then give them tons of water and end up with root rot or just plain killing the plant . I hope this information helps you on your quest to becoming a grow master ! :D :D :D -Happy Growing!