It looks like ARCC's placing small secondaries more frequently rather than large secondaries less frequently. It's a a wise move in my opinion, since the large secondaries had been priced excessively low while the smaller offerings are much better priced.
The stock may be down 3 days in a row, however remember the offering of the new shares were priced at $19.95. Until these shares are in the market stream the price will likely hang around present value for a few days. This a buy-hold for the yield! any weakness is an opportunity to buy more!
Secondaries are the common method for BDC's like ARCC to acquire new capital and grow. They're legally limited from carrying more than a 1.0 debt ratio, so when they find new deals that need new capital, they get it this way. They'll likely pay down debt, freeing that capital for use in future new deals.
It's not like a traditional company, where new shares are dilutive to the existing shareholders. Capital is ARCC's product, and they've just convinced Wall Street to pay $19.95 for something that technically isn't worth that much :-)