Solids and Favours lying with his Head to one Side

Hi Helen

I have two short questions for you ...

My five months old son started on two solids a month ago, at noon and in the evening, followed by breastfeeding. When is it time to introduce a third solid?

He favours lying with his head to one side, which has made his head a little lopsided. As recommended, we have laid him on the other side and it has improved. My question is when does the head become harder?

I take this opportunity to thank you for a wonderful website.

Best regards
Lone