I just can't imagine that it's watered too much. It's pretty good drainage in the soil. But, it has gotten worse the last couple of days and they did get watered a lot the past two days.
They are in full, full sun. There are several varieties. The worst are the lettuce leaf and sweet basil.
I'll give the nitrogen a try and let it dry out a bit this week. Thanks!
I have the worst luck with basil. Everything else seems to grow really well, despite many mistakes that I make.

Sometimes the leaves turn yellow do to over watering. Thant might be the issue with your plant.

I looked hard today. I think the stems are rotting. It does look like deeper in the soil it's pretty damp. I'll be out of town for a few days and it's really hot this week so I'll let it dry out. Hopefully, will be alive instead of dead when I get home!

I've got some basil plants (the first I transplanted outside) that are suffering from "failure to thrive," and I'm betting that my problem is that I put them out too soon while we were still having cool days and almost cold nights. Basil HATES the cold. I've decided that I'm simply going to have to dig them up and either direct seed now that it's warm or get new plants.

I think it is a combination of iron deficiency and too wet poor drainage. When I checked the soil it was wet about 3 inches down even though the top few inches was dry. Also, after asking the question the leaves began to get more signs of iron deficiency.
I may have lost the thai basil but I gave iron supplement and seaweed solution to everyone and stopped watering for a week. Everybody looks a little better.
Good news is that I held off planting all my other basil plants while trying to figure this out. I just planted them this week and last in different garden sections (several with tomatoes, a few on the side of the house in my winter lettuce garden) and they seem to be thriving, even having grown in the few days since transplanting.
I would really, really like to have enough basil this summer to put some in the freezer with EVOO/garlic. I like basil more than any other herb, almost more than any vegetable. If I could only grow one thing it would probably be basil and it's been my nemesis forever.
Okra got eaten by a bunny this week, BTW and apparently bunnies don't like basil, LOL!

Check the temperature, especially nighttime temps. Basil needs warmth to prosper. Protect it from cool weather until nighttime temp stays at 55F or better. If temp is not the issue, you may indeed be watering too much. Test the soil by poking your index finger down to the second knuckle, if it comes out dry, water thoroughly but allow to drain - do not let it sit in water. Continue the "knuckle test" until the plants are well established.

Hi Tracy,
Good to see it's doing better.

I do think it was over watered. I'm in Tucson, I have basil that came back from last year, Up until a week ago it was only getting rain water! Now that our temps are up and I planted the bed with lettuce I water it daily and it's doing great.

Good luck with the rest.

JoJo

Downy mildew. Not treatable. Pull out the plant and don’t put any bad in that spot for four years.

Hi, can basil grow indefinitely, assuming I have warm climate throughout the year? Mine have reached about 15 inches high after about half a year with regular pruning. There are less leaves now and the central stem has turned woody.