I would let this batch go, get yourself organized for the next nest. Beef-up the parents' diet with cyclop-eze (if you're not already) ,,, improved diet made a big difference with the quality of my Occ eggs & fry.
There are a few places online that will get you rotifers quickly, however, having ordered from all of them at one point or another, I found the rotifers from aquaticeco.com were the best value for money, by a long way,, I got 5 times more rotifers per dollar than everywhere else. Some well-known retailers (no names) sent LAUGHABLE numbers per litre compared to what I got from Aquatic Eco.
Their customer service is also unequalled IMO,,, I ordered some rotifers and they arrived a day late,, I lost a lot of fry,,, I complained,, and they comp'd me the entire order,,, including shipping,,,which cost them over $100 to keep a first-time customers happy. Pretty impressive.
They don't offer rotifers overnight any more,, but I'd still buy them there if I needed some,, I'd just have to order 4 or 5 days in advance.
Good luck with them,, not many folk are tank-raising nigripes because of their very slow growth-rate.
Did you take any pics of the nest?