I had a similar problem recently but mine was a lot less severe. While researching I come to the conclusion that my issue was a CalMag deficiency. They got stunted and wouldnt grow anymore. Once I gave it 1 tsp of CalMag per 1 gallon of distilled water they have started growing again and they look much healthier. But over watering can cause some serious issues too. That would be my first thought since u had no drainage holes for some time. Wait until the soil dries out then try to treat it for CalMag. You dont have to take my word tho I am also a new grower on my first time. I have researched a lot tho.