The plants look great to me. Depending on your medium and personal preferences, watering can be done several times a day or weekly if they don't need more water prior to that. I water daily (5 gallon buckets w/ Promix) and will get wilting if I let it go for more than 2 days, but every plant and medium is a little different as far as water retention goes. If you can go 7 days without watering, I would be concerned about the excessive water being held in the medium. I can't tell the overall size from your photos, but a mature plant goes thru a lot of water, at least in my experience. What are they being grown in?
I just saw that you are growing in a metal container with no drain holes. That is an invitation to disaster, in my opinion. Without the holes, O2 will have difficulty reaching the roots and the chance of them getting flooded/suffocated is pretty high. It can be done, but is difficult to grow like that and can cause a lot of problems. Bottom drainage is very important, at least in my setup.