Possibly stress related but it is not uncommon to give birth to only a few fry. I believe this happends because of either :
Its a young fish & its the first birth
Stress can be an issue & they can abort the birth until they feel comfortable again
The fish is not properly conditioned for breeding
Ive had 5 different batches off 3 different moms in only 2 months & each birth & the way they birth has been different each time
Also my guppy mom had her last batch 5 days ago & she looks like shes ready again but she wont drop any until the very last day, like ive had 3 batches off her now
The fry wont/cant eat food that is too big. I found for the first few days they will eat Spirulina powder or a liquid food,Such as Liquifry but this is very messy & needs regular water changes.
After day 3/4 they will eat flake if it is small enough for them to eat. They are always hungry