Weedy, holey rhubarb.

[Marb67]

My rhubarb is in full sun, deep, rich moisture retentive organic compost but the stems are thn and whispy with lots of holes that are not slug damage. Dug into the soil and found a couple of vine weevil grubs but the roots are still ok.

What is wrong with this as I am feeding with chicken manure and watering regular. Drainage is fine.