Are they small for 4 weeks?

They are just fine. If you want to be sure your light at the canopy is enough. Download the app PPFD Meter off the google or apple store onto your smart phone. Use the PPFD & DLI selection, and put the phone's selfie camera beside one of your tops at the canopy height and look at the PPFD number. For flowering plants like yours you should be upward of 900 to 1000 PPFD. No more unless co2 is being used. If it's less than 850 PPFD, then increase your dimmer or lower your light till you hit the 900 to 1000 ppfd target.

They look perfect man! Just let them be, I m sure you'll get some fat and dense buds, happy growing!!

Looks very good. Have patience.

Don't worry, your buds look perfectly fine ☺️ They will start to fatten up soon