Growing garlic for the first time

I have been criticised by a friend for growing my garlic in the tunnel they said it will be to warm, well my tunnel has the main door open and a mesh door closed it also has the mesh window at the other end, temperatures have been 5’C and less these last few weeks. Anyway today I noticed a number of the outer green shoots had started to turn yellow maybe a lack of water, I checked the soil it was not dry but I gave them a watering anyway . As I have never grown garlic before any comments would be welcome please. I can get some photos and post tomorrow