What's wrong with them

Looks like to many plants in one pot! Still looks awesome haha I used to grow outdoor in secret and very rarely did I ever get a plant to look that good! Next time try one plant in your barrel, certain cover crops are great just try and keep one large root mass in one barrel or pot and things will improve tremendously

Tip noted. being a beginner I really need some pointers how long to harvest these buds?

Very hard to tell without more clear pics with a decent lens, how long have they been in flower? And also I saw some webbing on bud in one of your pics maybe just a garden spider or something but could be mites.
How do the trichomes look to you if they are all cloudy your in harvest window, if you want couch lock let them go until more amber.
Also that strain looks very leafy might be hard but it’s better to find and make sure your looking at the calyx trichomes and not the ones on the leafs