Have a poke in the soil with your trowel, I suspect it may be on the dry side. As we are now heading into a period of greater growth, plants will use more water and I am moving to a 10-14 day time interval at the moment. It varies with the weather and we have had some dry winds recently, from the east and north west, which pull moisture out of tunnels.
We are finding very few slugs when picking, a sign that we have not been overwatering! I have watered twice since late November, enough to thoroughly wet all the soil.