Sadly, culling is part of breeding....Since we use closed systems it is up to us to cull the unhealthy, weak, small that would naturally be culled in the native ecosystem. By culling the weak, small and unhealthy will help your other fry grow strong. Also, IMO/E-especially for new hobbyist you should cull your fry down to a more manageable number. Quality-vs-Quantity....
Tell us more about your tank you have your fry...size, filter, live plants, additives, temp, what are you using to retain the heat/humidity over the water, how much and how often are the water changes.
How often and how much BBS are you feeding and how you are hatching and collecting to feed.