Help! My 10 month son hasn’t been gaining weight since he was 6 months old.

My 10 month old son is teething and has hand foot mouth disease so he has low to no appetite at all. It’s been 2 weeks he refused to be spoon fed and extremely picky what he eats. He won’t eat his baby food and he hasn’t been gaining weight since he was 6 months old. We’re desperate and worried why he doesn’t like his baby food anymore. We tried yogurt, purée, porridge, etc he just won’t eat them. He’s seem to be recovering. We need help how to get our son to eat solid and gain appetite again. Any tips greatly appreciated. Many thanks. Sincerely Worried Mom.