My 6 month old baby doesn’t eat

He eats average 15oz a day. Yes very low. He’s still “healthy” because he’s active and is gaining 0.5- 1 pound a month. He’s a a very small baby and is only 15 pounds.

I’ve tried countless doctors, feeding therapists, hospital, all of that. He doesn’t have a physical issue at all.

I just want my poor baby to be healthy and grow and gain weight. Will solids help my babe gain and get nutrition?