It looks like it's in a pot. How long has it been growing in the pot, what kind of fertilizers do you use and what is the soil like? Where are you and what kind of temperatures have you had?

Too much sun would cause the leaves that are in direct contact with the sun to turn yellowish / whiteish, including the leaf veins. The other leaves would remain dark green. On the other hand, leaves that do not get enough moisture will turn brownish from the edges inwards.

Watering once a week in a pot sound like not enough considering we are in June so, test the soil and give it about 1/2 to 1 gallon when the soil feels dry or almost dry. Plastic pots can get quite hot so make sure you do not expose the plant to direct afternoon sun. Make sure that they get shade starting around lunch time or earlier.